Research Call Dropping Syndrome In A Mobile Router Connection Used In A Vehicular Environment
With the emergence of mobile automobile internet routers in the past five years, theorists and visionaries have begun to picture a world for their widespread application. From transportation infrastructure and inter-vehicular communication to mobile conferencing and business applications, the ability to access the internet during transportation is an increasingly valued concept. Yet mobile phones have internet services and cellular providers offer broadband 3G and 4G options, so why amidst all of this integrated technology does the mobile router become such a key component? Efficiency and performance. By leveraging the strengths of an integrated urban infrastructure and utilising multiple access points, the bandwidth and quality of service associated with mobile internet routing is rapidly increasing. Due to the rapid rate of motion and exchange, one of the most inefficient concepts within mobile routing is handover latency, a potential lag in network resources during which packets of information are exchanged between the mobile router and the new access point. This research will provide a broad spectrum of theory and evidence regarding opportunities for moving towards a soft handover, undermining the performance losses and network degradation associated with hard handover switching behaviour. Further, predictions will be made for the future of mobile automobile routing services, highlighting particular concerns that must be remedied in the coming years in order to enhance industry performance.
1.1 Research Problem As internet integration and communications convergence is increasingly impactful on human existence, the exploitation of new and emergent technologies for increasingly mobile applications continues. One of the most debated advances in recent years is directly related to the integration of mobile internet into automobiles. With one leading firm, Autonet Mobile currently supplying a proprietary technology to several key automobile manufacturers, the merits of mobile routing continue to be validated through commercial value and consumer investment. From a technical standpoint, router-network communication protocol is relatively standard when a static relationship is established; however, once this relationship becomes mobile, the handover requirements due to mobile access points can result in a breakdown in quality of service (QoS) and connection dropping behaviour. Using the NEMO basic support protocol, a mobile router is able to use Mobile IPv6 to 'establish and maintain a session with its home agent...using bidirectional tunnelling between the mobile router and home agent to provide a path through which nodes attached to links in the mobile network can maintain connectivity with nodes not in the NEMO'. This brief explanation of a network architecture designed to maintain mobile consistency and reduce signal dropping behaviour is indicative of emergent technology in the mobile routing field, a capability with wide scale applications across automobiles, trains, busses, and other ground transportation networks. Although Autonet Mobile is the most public corporation currently working towards the development and implementation of mobile internet in automobiles, it is unlikely that such market supremacy will continue into the future. With expectations of more integrated automobile systems, particularly those related to navigation and intra-traffic vehicular communication (accident reduction schemes), academics such as Carney and Delphus are already predicting a rich, network-integrated future for mobile computing and internet applications. Considering that QoS for other diverse communication options including VoIP remains of particular concern in the mobile computing community, more in-depth analysis of connection management and performance in a mobile environment is needed. The concept of mobile routers and a mobile internet connection through intra-vehicular integration is foreign to many consumers, even in this era of diverse technologies and increasingly advanced network architecture. Therefore, the fundamental value of this dissertation may be linked to more predictive analysis of future applications and systemic evolutions regarding these emergent technologies. Through a comprehensive review of the existing academic evidence in this field as well as several examples of mobile routing technologies that are either currently in production are being field tested, the following chapters will firmly establish a rich, evidence-based perspective regarding technological viability, updates and version 2.0, and the future of mobile internet routing. 1.2 Aims and Objectives Although wireless technologies have a longstanding history in internet protocol and architecture, the complexity of handover behaviour and connectivity in mobile router service continues to challenge developers to reconsider the merits of their design. Accordingly, as 3G and 4G mobile broadband networks are expanded across metropolitan and surrounding areas, the flexibility of mobile routers and intra-vehicular internet use is increasing significantly. Simultaneously, alternative technologies including the Autonet Mobile router exploit such interconnectedness to maximise wireless performance, conducting mobile handoffs of service as vehicles pass from one cell tower to another. The scope of this investigation is based on emergent technologies and connection dropping behaviour during in-motion computing. Therefore, a variety of sources will be explored over the subsequent chapters in order to evaluate the progress made in this field, practical applications and their relative reliability, and future opportunities for redesign and reconfiguration of mobile routers. In order to govern the scope and scale of this investigative process, the following research aim has been defined:
- To evaluate the emergence of wireless router technologies for automobiles, comparing the connection dropping behaviour of mobile broadband networks and tower switching protocol in order to predict the viability of future applications and technologies.
Based on the variables addressed in this particular research aim, this investigation involves three primary data streams including evidence regarding the performance of mobile broadband routers and cards, the evidence regarding the performance of hand-off-based mobile internet access routers, and the opportunities for expanding this technology beyond its currently limited scope in future applications. As this investigative process involves the analysis of a broad spectrum of empirical findings in this field, secondary academic evidence forms the theoretical foundations of the background to this mobile internet problem. In addition, empirical evidence from actual network architecture is retrieved from existing applications of these distinctive technologies. Throughout the collection and analysis of this evidence, the following research objectives will be accomplished:
- To identify the underlying conditions which contribute to connection dropping behaviour in mobile internet usage
- To evaluate the structure of mobile internet architecture, highlighting the benefits and limitations associated with the various technologies
- To highlight theoretical and emergent applications for mobile internet connections, expanding the scope of usage beyond just web surfing whilst driving
- To offer recommendations based on the optimisation of network architecture according to a purpose-oriented protocol
1.3 Research Questions Based on the aforementioned research aims and objectives, there are several key research questions that will be answered over the following chapters:
- What expectations are manifested regarding mobile internet usage in vehicles, and how is such performance evaluated?
- What opportunities are there for integrating mobile internet on a broader scale for more strategic, vehicular purposes (i.e. navigation, multi-vehicle communication, etc.)?
- Are there specific benefits of a mobile broadband connection over tower handover behaviour and vice versa?
- What will determine the future of mobile internet and how will such variables be identified and incorporated into the network architecture?
1.4 Structure of Dissertation This dissertation has been structured in order to progress from a more general, theoretical background to specific mobile internet routing evidence. The following is a brief explanation of the primary objectives for each of the subsequent chapters:
- Chapter 2: Literature Review: Highlighting an academic precedence established in this field over the past two to three years, empirical studies and theoretical findings are presented and compared in direct relation to the research aims and objectives.
- Chapter 3: Research Methodology: This chapter seeks to demonstrate the foundations of the research model and the variables considered in the definition of the analytical research methodology.
- Chapter 4: Data Presentation: Findings from an empirical review of existing mobile router architecture are presented, highlighting particular conditions, standards, and performance monitoring that govern functionality and performance.
- Chapter 5: Discussion and Analysis: Retreating to the academic background presented in Chapter 2, the research findings are discussed in detail, offering insights into the challenges and opportunities associated with current network architecture and mobile internet protocol.
- Chapter 6: Conclusions and Recommendations: In this final chapter, summative conclusions are offered based on the entirety of the collected evidence, and recommendations for future mobile internet routing solutions are provided.
Chapter 2: Literature Review
2.1 Introduction There is a broad spectrum of academic evidence relating to mobile internet, network architecture, and operational protocol. This chapter seeks to extract the most relevant studies from this wealth of theoretical and empirical findings in order to identify the key conditions and components associated with effective and high performing mobile internet in automobiles. Further, evidence regarding connection dropping syndrome is investigated in order to highlight those deficient characteristics that continue to detract from the overall performance of these various networks. Ultimately, this chapter provides the background findings that will be compared with practical applications of mobile internet routers in vehicular scenarios in Chapter 4. This analysis is designed to not only introduce the academic arguments regarding the functional architecture of mobile routing and its widespread potential applications, but to also compare the principles and practices that have been discussed across a diverse range of technological interpretations. 2.2 The Background of Mobile Automotive Routers In 2009, emergent technology inspired by an increasing social demand for internet mobility and integrated online resources in automobiles began to make its way to the market. Carney reported on an American based firm, Autonet Mobile which viewed the future of integrated mobile wireless as handoff-based through existing cell towers rather than mobile broadband card-driven. In essence, this proprietary technology leverages a similar communications standard to the 3G and 4G broadband routers that continue to be offered by mobile phone providers AT&T, Verizon, Sprint, and others. Consumer analysis by Autonet determined that over 50% of consumers surveyed reported on a desire for internet service in their cars in comparison with just 16% who were interested such technologies in the early parts of the 21st century. Practical applications of mobile internet routers include direct streaming of navigation tools such as MapQuest and Google Maps to the vehicle or benefits for business customers which include mail and file transfer capabilities or even online information sourcing. Uconnect Web is the service provider which ultimately links the user through the Autonet router to the internet, offering data speeds that have been reported as comparable to 3G technologies. By default, the broadcast range is around 150 feet from the car, differentiating the flexibility of use in this technology from PAN architecture. Although the uptake of the Autonet router in such automotive producers as Chrysler and Cadillac was widely publicised, the general public reaction was not necessarily a market-shifting response. In fact, a leading analyst of direct competitor Ford would criticise the Autonet router early in its lifecycle, suggesting that many consumer will not see value in the investment in technology that is similar to that which they already pay for on their other mobile devices, especially when it is limited to the architecture of the vehicle. In spite of such predictions, by February of 2009, the Autonet router had received its first award from Good Housekeeping magazine for Very Innovative Products (VIP), a recognition that was directly oriented towards this new products potential value for families in its integration of multiple devices within a single wireless hub. In 2010, Delphus reported on significant increases in subscriber statistics, from around 3,000 vehicles in 2009 to over 10,000 by mid-2010, the direct result of strategic partnerships with such rental car giants as Avis and continued OEM partnering with Chrysler, GM, Volkswagen, and Subaru. In spite of the more commercial value of this concept, what is most relevant to the scope of this investigation is the proprietary handover management technologies that have emerged in the Autonet operating protocol. In fact, Delphus reports that because of contractual partnering with multiple wireless telecom providers, Autonet is able to maintain consistent web streaming with very minimal 'between tower' signal fading in urban spaces. Considering that handover processing and seamless transfer of addresses between towers is one of the technologies developed under the NEMO project previously introduced by Lorchat et al., the commercial value of such initiatives could potentially be expanded to include a much more integrated traffic architecture and communication network. In his exploratory evaluation of NEMO as a handover framework for mobile internet routing (particularly in multi-nodal vehicular applications for traffic navigation/communication), Ernst highlights particular challenges with maintaining quality of service under mobile conditions. In particular, he recognises that addresses must be topologically correct involving specific language designed to interface with a particular tower, an ability to change the IP subnet, and ultimately the change of location and routing directive. In order to maintain sessions and quality of service, Ernst introduces a communicative architecture based on a bi-directional tunnel between the home agent (HA) and the mobile node (MN), a connection which must remain dynamic and automatic whilst receiving bandwidth allocation from the access network. In particular, such early work on the NEMO architecture established specific performance requirements which included permanent and un-interrupted access to the internet, the need to connect simultaneously to the internet via several access networks, and the ability to switch to best available access technology as needed. By default, this flexible architecture provides the following predicted benefits:
- Redundancy which reduces link failures that arise in mobile environments
- Ubiquity which allows for a wide area of coverage and permanent and un interrupted connectivity
- Flexibility that receives specific policies from users/applications and price-oriented competition amongst providers
- Load sharing to efficiently allocate bandwidth, limiting delays and signal losses
- Load balancing
- Bi casting
The value of NEMO protocol is that it allows for shifting points of attachment in order to achieve optimal internet connectivity. When a mobile node is on a foreign network, it is able to obtain a local address termed Care of Address (CoA) which is then sent to the home address for binding. Once the binding is complete, the HA 'intercepts and forwards packets that arrive for the MN to the MN' via the ubiquitous tunnel to the CoA. It is this binding and re-binding of different CoAs during mobility that ultimately allows for improved QoS, restricting the number of dropped connections and maintaining persistent internet connectivity in all areas where call towers can be accessed. Within this architecture, binding updates are used to notify HAs of a new CoA, whereby the HAs send a binding acknowledgement that may either be implicit (no mobile network prefix option) or explicit (one or more mobile network prefix options). It is the underlying use of the IPv6 architecture which Moceri argues allows for more efficient tunnelling and more consistent security than IPv4 options, due to the IPSec, the tunnelling mechanism, and the optional foreign agent usage. 2.3 Mobile Routing and Network Architecture One of the more recent evolutions of the mobile routing protocol is based on NEMO (Network Mobility), an architecture that is designed to flexibly manage a single or multiple connections to the internet, even during motion. Based on the standardisation of protocol and architectural features by the IETF in recent years, NEMO is quickly becoming a viable means of extending internet services, diversifying online communication, and establishing a mobile link between variable nodes. In their recent analysis of this architecture, Lorchat et al. suggest that IPv6 was designated as the best fit solution to the network mobility problem, allowing for the mobile router to change its point of attachment to the IPv6 internet infrastructure whilst maintaining all current connections transparently. The authors introduce a model-in-development application of the NEMO architecture suggesting that a singular home agent would act as a maintenance and exchange module, retaining information regarding permanent addresses of mobile routers, temporary addresses, and mobile network prefixes. The primary challenge associated with intra-vehicular mobility of an internet connection in this particular challenge is that the automobile needs to perform handovers between wireless access points. Although such research is valuable from an early architectural standpoint (i.e. 2006 technology), the accessibility of wireless technology provided over mobile telephony suites via 3G and 4G technology is far advanced from a point-to-point handover protocol. In more in-depth review of the NEMO technology, other researchers have endeavoured to identify the key limitations and opportunities that are associated with particular orientations and architectural standards. Chen et al., for example, based their research on the viability of applying NEMO BSP within public transportation in order to provide mobile internet for all passengers. This research is extremely valuable for the development of effective router protocol in the future, as the authors propose that in order to overcome the multihoming problem (i.e. a need to access multiple types of networks in order to reduce downtime and connection dropping), multiple router types could be linked wherein each router is equipped with just one type of interface could be viably used to improve quality of service. For their research, the mobile router is equipped with WLAN, GPRS, and CDMA interfaces simultaneously and an inter-interface handover algorithm is proposed for the signal exchange whilst performance during handover is measured and analysed. To accomplish such network architecture, the authors needed to introduce multiple CoA registration under which bi-directional tunnels could be established for each of the three networks without having to identify one network as primary over the others. Post analytical conclusions suggest that MIPv6 and NEMO BSP are inappropriate for 'delay sensitive applications due to handover latency of more than 1.5s'; however, multiple interfaces and different internet service providers can offer a means of transferring traffic smoothly from one interface to another. 2.4 Alternative Schemes and Personal Access Networks In spite of a more narrowed broadcast scope, wireless personal access networks (WPANs) are increasing in popularity, basing short range wireless communications on two distinct standards including IEEE 802.15.3 (High-Rate WPAN) and IEEE 802.15.4 (Low-Rate WPAN). Accordingly, WPANs are defined around a limited range personal operating space (POS) that is traditionally extended up to 10m in all directions around a person or object, stationary or motionless. LRWPANs are typically characterised by a limited data transmission rate of between 20 kb/s to 250 kb/s, requiring only minimal battery power and providing a transfer service for specific applications including industrial and medical monitoring. Conversely, HRWPANs offer a much higher rate of data transmission from 11 Mb/s to 55 Mb/s and are suitable to allow for the transmission of real time video or audio and providing the foundation for more interactive gaming technologies. In HRWPAN protocol, the formation, called a piconet, requires a single node to assume the role of the Piconet Coordinator (PNC) that is designed to synchronise other piconet nodes, support QoS, and manage nodal power control and channel access control mechanisms. Node functionality in the piconet architecture is defined as follows:
- Independent Piconet: Stand-alone HRWPAN with a single network coordinator and one or more network nodes. Network coordinator transmits periodic beacon frames which other network nodes use to synchronise and communicate with network coordinator.
- Parent Piconet: HRWPAN that controls functionality of one or more piconets. Manages communication of network nodes and controls operations of one or more dependent network coordinators.
- Dependent Piconet: Involve a 'child piconet' which is created by a node from a parent piconet to extend network coverage and/or to provide computational and memory resources to the parent.
The value of the PAN architecture is based on its high mobility and innate flexibility, allowing for single devices to operate as mobile routers, providing internet access to multiple devices. Moceri predicts that by integrating NEMO protocol into PAN network architecture, it is possible to use a particular device such as a mobile phone to provide continuous access to a variety of other devices. Ultimately the future of this technology is directly linked to inherent efficiencies that are associated with network operations and architecture, Ali and Mouftah reiterate that in order to maximise PAN uptake in the future, a variety of protocol-based concerns must be remedied and transmissions should be become increasingly efficient. One instance of inefficiency that was identified by their empirical analysis indicated that there is a threshold value for the exchange of packets that once violated results in an accelerated rate of rejection. This is a serious concern that must be addressed through design and development of the PAN standard. 2.5 Summary This chapter has introduced the background concepts associated with mobile wireless internet in modern automobiles. In spite of the fact that the market is limited to just one strong and integrated firm, it is evident that over the long term, opportunities for competition and alliance from other providers and service agencies is increasing. Consumers continue to demand additional connectivity and an increased standard of internet access. Unprecedented potential for redefining the future of internet mobility is currently manifesting itself throughout this industry and as such leading agencies as the IETF continue to expand their investigative process, the expectation of advancement is rampant. Ultimately, one of the first challenges that must be addressed within this field is that of handover technologies, an area of mobile internet that involves the majority of performance-based losses. By focusing on such key transitional periods in the access process, the opportunity for systemic optimisation will be greatly enhanced. The following chapter will provide background regarding the research methods that were employed in the analysis and discussion of practical handover problems and their review in this field.
Chapter 3: Research Methodology
3.1 Introduction This chapter presents the research methods that were employed in the collection and analysis of evidence regarding the viability of mobile routing technologies across intra-vehicular applications. Focusing on an academic precedence in this field as well as guidance from theorists focusing specifically on data collection methods and analytical techniques, background is offered to validate the methodological decisions made over the course of this process. Ultimately, specific evidence regarding research architecture and the various components integrated into the research process will be addressed, as well as particular, strategic and incidental limitations affiliated with the focus of this study and a multi-stream analysis of complex data. 3.2 Research Methods The majority of research in this field focuses on case study evidence in which network architecture, internet protocol, and various limitations and opportunities are investigated via case study examples. Chen et al., for example, utilised three different mobile routers in order to investigate handover behaviour and network performance in a mobile vehicular network. Such experimental data serves to validate best fit programming and architectural features, measuring handover time for packets of information across different conditions including between GPRS and CDMO and MR in NEMO BSP. Although the value of such analysis was recognised early in this research process, the focus of this analysis is to differentiate between hard and soft handover architecture, a condition that can be evaluated within the context of existing technology. Therefore, the experimental research method was determined to prescribe too wide of a scope of research for this study and was eliminated from the available options. Other academics have leveraged the past theories and studies of other empiricists in order to conceptualise the foundations of a future defined by mobile vehicular internet connections. Gerla and Kleinrock, for example, explored a variety of different concepts on Inter vehicle communications (IVCs) and their applications in hypothetical transportation system architecture. Such research involved content analysis from past studies in which empirical findings and theories are cited as a means of predicting future adaptation and adjustment within the global architecture. Based on the research model presented in this study, it was determined that a comprehensive review of leading theories and findings in this field that were directly linked to the aims and objectives of this research would be a valuable research methodology. Based on the review of past academic methodologies, a comprehensive content analysis of recent findings from empiricists and academics in this field was determined to provide a best fit research methodology. Krippendorff argues that analytical constructs 'ensure that an analysis of given texts models the texts' context of use', limiting any violations regarding what is known about the conditions surrounding the text. Due to the complexity and technological variability of this topic, it was important to restrict interpretation of the findings and academic perspectives to their relative context, the foundations of which were ultimately defined early in the reports. From the application of mobile routing in pedestrian circles to vehicular mobile routing for public transportation purposes, the context was determined to be a driving factor in the protocol and architecture chosen for handover schemes in mobile internet connections. A total of six unique studies were identified as directly relevant to the investigation of soft handover technology and applications, and the general findings from these studies were then extracted and integrated into the following chapter. This data is directly relevant in predicting evolution in this industry and detailing opportunities for integrating soft handover technologies in order to optimise system performance in the future. 3.3 Ethical Concerns and Limitations The evidence presented in the content analysis was all extracted from journal publications that are widely available to the public through multiple databases and online retrieval sites. Therefore, it was determined that based on this research method, there weren't any ethical concerns relating to the data. There were, however, limitations imposed on the scope of the studies researched in order to ensure that the focal point of these analyses was directly oriented towards handover protocol and mobile routing architecture. The imposition of such limitations proved valuable because they allowed the research to be focused on specific conditions, outcomes, and opportunities regarding this topic that will be extremely relevant in future developments in this field. 3.4 Summary This chapter has presented the research methods that were employed in the collection and analysis of secondary evidence regarding this widely debated topic. Recognising that inconsistencies in the review of one or two studies could result in innate research bias, six different studies were chosen from varying areas of focus in mobile routing technology. The findings are presented and discussed in direct relation to their independent context, with the exception of a few correlations that were drawn in order to link concepts and industry standards. The following chapter will present the findings from this content analysis in detail.
Chapter 4: Data Presentation
4.1 Introduction This chapter presents a broad spectrum of academic theories, evidence, and predictions regarding the evolution of the mobile internet architecture. Whilst oriented towards the application of this technology in modern automobiles, the findings from a review of leading theorists in this field have demonstrated that the concept of handover management and strategic redefinition in mobile networks transcends the limited scope of this problem. Therefore, although current routing systems available in the marketplace may integrate different technologies or architecture than those discussed here, the focus of this research is ultimately on the evolution of the mobile handover between access points from a hard, delay-limited process to a soft, dynamic and integrated process. 4.2 The Current Problem The modern consumer demands immediacy in all aspects of their life, from food procurement to entertainment to communication. As the heterogeneous architecture of an integrated, internet-oriented society continues to affect product choices and consumer values, the notion of a functional, high performing vehicular router has quickly become integrated into several leading automotive producers in the past several years. Labiod et al. define a mobile router as 'a mobile node which can change its point of attachment to the internet and then its IP address'. Similarly, mobile networks involve a 'set of hosts that move collectively as a unit', leveraging a mobile router to perform gateway tasks and provide connectivity for all nodes within the mobile network. Based on the IETF conceptualisation of NEMO, a protocol that allows dissimilar technologies to connect simultaneously to mobile networks, handover latency is rampant in mobile exchanges, the direct result of innate deficiencies within the system architecture itself. As a result, many academics have undertaken a variety of strategies in order to identify and prescribe more flexible architecture for mobile routing, attempting to reach a best-fit position whereby a universal standard based on soft, integrated handover protocol can be incorporated into this growing network of variable devices. 4.3 The Soft Handover The following analysis will explore the particular handover techniques that exist in mainstream academia, highlighting the strengths, weaknesses, and similarities of each in order to identify what is perceived as an industry standard for next generation mobile architecture. As previous evidence has introduced many of the concerns, conditions, and predictions regarding the mainstream applicability of a more flexible, dynamic network architecture in mobile routers for automobiles, this evidence is designed to bound the future of these architectural predictions according to optimisation schemes based on a continuous connection objective that will ultimately facilitate quality of service. 4.3.1 Kaur and Chopra: Next Generation Mobile IP In order to initiate this investigation regarding proposed alternative handover schemes, the general interpretation of this problem has been extracted from Kaur and Chopra. These authors suggest that due to an evolution of consumer preferences, in the modern marketplace, there is an expectation of network omnipotence, whereby heterogeneous communication channels remain open without being timed out across an integrated network of WLANs and WPANs. It is for this reason that the soft handover, an exchange of agents whereby limited performance degradation is incurred, is integrated into the standard network architecture and protocol of the future. The architecture of this particular soft handover strategy involves the introduction of a duplication and merging agent into a similar connection to that employed in the NEMO network. Kaur and Chopra describe this process in stages as follows:
- A temporary address is obtained by the mobile router when it first connects to the network.
- The address is registered with the HA and a duplication and merging agent (D&M)
- Packet transmission from D&M agents to MR involves two local CoAs wherein a new IPv6 packet is created with the same payload information.
- The duplicated version of this information is then transferred to the MR.
- To protect against data loss, the packets are differentiated by the DIO (Destination identifier field), the presence of which will stop the IP packet duplication process.
- A primary threshold is used for the soft handover whilst the secondary threshold is used to avoid degradation of signal strength.
- Handover occurs if the signal strength threshold level is less than the reference threshold level.
Through experimental analysis of the soft handover mechanism, Kaur and Chopra were able to identify whether performance improvements would occur when compared with LAN, hard handoff statistics. The evidence from this particular study is offered in Figure 1, highlighting the nature of changing packet transfer speeds and consistency across all three networks. For the first (a), the wired LAN UDP performance is benchmarked, allowing for comparison in foreign wireless networks. For (b), a normative MAC-only handoff influence on UDP performance is introduced, and for (c), the MAC/Mobile IP handoff influence on UDP performance is demonstrated. The results indicate that through soft handover technology, the likelihood of maintaining an improved handover with more limited connectivity losses. Although limited in its scope and scale, this research is indicative of the thought process in the academic community regarding the evolution and emergence of more efficient technologies for handover protocol in mobile networks. 4.3.2 Yang et al.: Integrated WiMAX and WiFi Network Driven by a realisation that WiFi is innately deficient in its coverage range and its bandwidth capabilities, Yang et al. suggest that a more viable alternative would involve the integration of an emergent technology termed the WiMAX network. Although not directly related to automotive applications (the authors are more concerned with intra-university installations), the handover protocol discussed in this investigation is relevant to this study and offers valuable insights into the challenges and concerns associated with mobile internet protocol. In attempting to establish a persistent service standard, Yang et al. recognise that user mobility is likely to follow some common form of geographic patterns (i.e. due to structural interference, popular common spaces, etc.). In order to facilitate the handover process within this diverse spectrum of spaces, the authors propose a scheme that integrates geographic mobility awareness, a purposeful network conditioning strategy that is designed to conserve mobile device energy demands by reducing the handover frequency according to moving speeds and signal strengths of the various site-specific routers. One of the important variables in this particular model is that home network preservation is of particular concern to the researchers, providing a means of reducing excessive handover and maintaining a soft handover protocol that eliminates the need for frequent network switching and thereby implies efficiency in terms of both user and provider resources. Figure 1 is indicative of the proposed integrated network wherein multiple mobile devices are able to connect within the scope of two layered sub-networks in order to maintain service during mobility. Although it is important to reiterate the fact that this integrated network architecture is based on pedestrian or relatively local travel patterns, the handover behaviour outlined in this model is extremely valuable and demonstrates the feasibility of more selective exchange practices. For example, Yang et al. integrate association failure probability into their simulation model in order to demonstrate the impact on the number of handovers that are completed. Aligned with the aforementioned research conducted by Chen et al., the authors are able to demonstrate that even when user motion has an impact on the overall bandwidth factor of a given network, by combining multiple networks into a single system, the ability to leverage the strengths of alternative broadcasts is enhanced. In fact, Yang et al. suggested that for non-integrated WiFi/WiMax mobile devices, quality of service suffered greatly during traditional phone motion due to limited accessibility to low bandwidth WiFi networks. The primary outcomes of this integrated research model included a conceptualisation of a human-oriented network handover protocol that ultimately eliminated unnecessary exchanges, reduced network scanning, and avoided too frequent interface switching. 4.3.3 Becvar and Mach: Fast Predicted Handover Although similar to the research offered by Yang et al., the Becvar and Mach model of handover focuses only on the WiMAX network in an attempt to prescribe a soft handover procedure in order to replace more traditional hard handover standards. Recognised as the 'break before make' handover protocol, the authors suggest that the hard handover can result in significant quality of service issues as the connection with the current base station is severed before a new connection is made at the target base station. By separating the handover process into multiple stages, the network is able to offset any potential delays by accessing the most viable base station. Becvar and Mach suggest that during and interleaved scanning process, the mobile router seeks a suitable target for the next base station, a condition that is ultimately either triggered via particular conditions (i.e. low bandwidth, low signal, etc.) or at periodic reporting periods that are predetermined. Upon detection of a viable base station (according to channel parameters and QoS), the handover process is initialised and the connection with the serving base server is closed. To offset this handover interruption period, Becvar and Mach argue that multiple base servers may be communicated with simultaneously, a non-affective dialogue between the mobile server and a diversity set of base servers. The only time during a soft handover that a delay would occur is if the diversity set were to only contain one base server option; however, when increased to two, then the delay is eliminated and the interruption of service is averted. With this general definition of a soft handover alternative on the WiMAX network as proposed by Becvar and Mach, it is important to address the specifications of their new network architecture, highlighting the particular features and conditions that differentiate this model from hard handover protocol. Defined as a Fast Predicted Handover (FPHO), the authors indicate that their technique is based on the modification of management flow messages at the MAC layer and a predictive functionality wherein target base servers are evaluated and the feasible connection is identified. Ultimately, the soft handover procedure presented by these authors is identified as a highly viable alternative to hard handover standards, leveraging prediction results through a MAC management message that initiates messages exchanged between serving and target base servers, clarifying pre-entry qualifications and verification of the server accessibility before determining that the scenario is optimal. In essence, this particular strategy reduces or eliminates any periods of interruption, undermining any conditions associated with call or connection dropping syndrome. 4.3.4 Kim and Koh: Performance Enhancement of mSCTP The complexity of the heterogeneous network environment is continuing to increase, the direct result of multiple technological segments, capabilities and standards that interlink within an enigmatic standard known as the 'internet'. Kim and Koh suggest that next generation wireless networks have evolved towards an IP-based heterogeneous network architecture that innately complicates the handover processes as a direct result of a conflict between static and dynamic variables. In order to circumvent this problem, the authors suggest that Mobile Stream Control Transmission Protocol (mSCTP) incorporates multi-homing and dynamic address reconfiguration features to improve the handover process. Similar to the model proposed by Becvar and Mach, this technique involves the dynamic integration or deletion of a new IP address to or from the current SCTP association as the mobile node (router) moves across different IP networks. Under such switching behaviour, the mobile node establishes a new primary path for a detected base station, eliminating (or limiting) the need for the old IP address from the past base station connection. Due to the heterogeneity of modern network architecture, WLAN and 3G wireless access networks are frequently integrated into a singular user network during their movements throughout the spectrum of provider resources. Kim and Koh suggest that due to a disparity in network bandwidth and/or transmission delays between these two very distinct wireless networks, performance degradation is frequently significant and must be mitigated. This division in performance is defined as 'asymmetric link characteristics' or the 'packet reordering problem' because of the divergent management standard across networks that could even result in lost data packets during re-prioritisation of particular networks. Figure 3 demonstrates the packet reordering problem when switching from a 3G network to a WLAN network, wherein replication of packets results in performance degradation of the mSCTP handover, or a slow start phase. The converse of this exchange (from WLAN to 3G) is also problematic, as seen in Figure 4. Kim and Koh suggest that because the WLAN network in this theoretical model is at the boundary of the network in the middle of the handover, the old link may become unstable. The realisation of packet loss due to the degradation of the exchange can only be achieved in the 3G network when the retransmission timer is expired, a problem in heterogeneous networks termed the 'retransmission timeout problem'. Ultimately, this retransmission timeout leads to the degradation of the handover performance as the bandwidth of the new path cannot increase until the retransmitted data has been acknowledged. In direct response to this handover problem, the authors propose the development of a new protocol whereby all outstanding data packets are retransmitted over the new primary path after the path is switched, avoiding packet reordering and improving the transmission performance during handover. In spite of the fact that this particular scheme still relies upon a hard handover architecture, a more dynamic packet management standard is innately effective and preserving the quality of service during uni-directional handover activities for mobile networks. 4.3.5 Yang et al.: Soft Handoff Support for SIP-NEMO Application perspectives continue to affect the design of network architecture, particularly in mobile vehicular applications. Yang et al., for example, began with a realisation in spite of steps taken by the IETF to resolve the issue of NEMO handoff delays and quality of service deficiencies, there are still alternatives that must be considered in order to ensure optimal evolution of this protocol in the future. By comparing two different approaches including MIPv4-NEMO and SIP-NEMO, the authors attempt to resolve the handover challenge, embracing the concept of soft handovers through strategic design of data and nodal management techniques. For the MIPv4-NEMO, Yang et al. suggest that the triangular routing problem between the passing of packets to the home agent then to the home agent of the mobile router and finally to the router's current address. By improving this handover protocol to reduce the delay through a tunnel between the previous access router and the new access router before handoff takes place, the authors suggest that packet transfer is nearly immediate because of the established link between routers. Consequently, however, within the FMIPv4 architecture, it is noted that packets are likely buffered in the new access router until the link layer between the new access router and the mobile router is established, a condition of delay similar to that introduced by Kaur and Chopra as well as Becvar and Mach. An alternative model proposed by Yang et al. termed SIP-NEMO or session initiation protocol (SIP) in NEMO involves a mobile gateway. When the SIP client moves into a mobile network, the IP address is registered to the mobile gateway, and the gateway then registers itself to the home server. If a corresponding node desires communication with the SIP client, then the mobile gateway serves as a translator between the two, establishing an end-to-end communication path with the SIP client. In spite of its benefits, the authors caution that SIP-NEMO does involve handover delays and is not suited for real time services. 4.3.6 Huang et al.: Packet Forwarding Control for Vehicle Handover Although the commercial applications of mobile routers for personal vehicles and consumer-centric net surfing capabilities have been widely discussed in academia, one of the most valuable applications in mobile routing and mobile internet communication is for intelligent transportation systems (ITS). Huang et al. define such systems as an 'application which combines electronic sensors, computer hardware and software, and communication technologies to improve the effectiveness of the transportation system'. As previously addressed in this investigation, vehicular applications are diverse, and for both consumers and social administrators, maximising the value of intra-vehicular communication is a primary objective in the future. Figure 5 highlights a more basic conceptualisation of vehicle communication networks presented by Huang et al., indicating multi-directional communication between home and the vehicle, vehicle to vehicle, and destination to vehicle (i.e. GPS). Mobile carriers continue to offer mobile routing services through 3G and GPRS networks; however, Huang et al. argue that these systems have a high upfront and operational cost and likely operate with a low transmission bandwidth. Alternatively, vehicles could operate on an 802.16 based wireless communication infrastructure within which roadside base stations (BS) could provide multi-nodal connection points for travellers. Due to the rate of travel of most vehicles within modern road networks, the switching behaviour of the on board router is incredibly rapid, relying upon multiple BS modules in order to maintain a steady internet connection during transport. Huang et al. caution that due to handover latency and data transfer problems, a new, more dynamic and forward-seeking technology is needed. The authors propose WiMAX, a similar alternative to that proposed by Yang et al. in their review of pedestrian network navigation and handover optimisation. In order to maximise the effectiveness of the WiMAX router, Huang et al. propose that forward seeking handover prediction can assist with the establishment of a tunnel between the new access router (NAR) and the previous access router (PAR), resulting in a redundant transmission during handover. Figure 6 highlights the conceptualised forward seeking WiMAX network and demonstrates the triangular redundancy that may have a negative influence on the bandwidth allocation of the network. In order to offset redundancy and minimise performance loss, Huang et al. have developed a packet forwarding control (PFC) scheme in which a common ahead point (CAP) is identified and all packets are forwarded ahead of the exchange. The CAP is then able to forward the packets directly to the NAR, bypassing the triangular transmission through the PAR. Through empirical evidence, the authors tested their PFC scheme, determining that this control architecture would improve handover functionality, ensuring fast tunnelled packet delivery and a shorter bicasting path. 4.4 Summary This chapter has introduced a broad spectrum of evidence and content regarding the empirical modelling of mobile routing technologies and the integration of soft handover techniques that are designed to overcome many of the delays and restrictions associated with this emergent technology. For vehicular applications, there are a variety of complexities including the overall demand for the internet services (i.e. internet-car communication, traffic communication, GPS routing, etc.) that ultimately demand an efficient and effective routing mechanism. Although these multiple studies have presented several clear cut options for rehabilitating the state of handover practices, the difficulty associated with an evolving technology is that there is no singular solution or best practice. Instead, organisations will continue to embrace proprietary modifications of these various recommendations in order to establish market supremacy and consumer interest. The following chapter will discuss these findings in more detail and highlight the particular challenges that undermine the prescription of more standardised routing architecture for myriad applications in the modern world.
Chapter 5: Discussion and Analysis
5.1 Introduction The previous chapter introduced the work of six distinct academic visionaries seeking to advance the field of mobile routing and intra-vehicular internet access. Although several of these presented solutions were similar, the process for identifying and testing these architectural standards was diverse. From pedestrian mobile routing to public transportation internet provision to vehicular travel, these insights have presented a case for handoff rehabilitation and standardisation within this diverse technological environment. The subsequent sections will address these findings in more detail, relating this evidence to the particular concerns regarding immediate improvements to routing technologies that have been applied through the Autonet routing system. 5.2 The Future of NEMO Mobile Routing The vision of NEMO based mobile routing protocol is relatively consistent within the scope of those researchers who have accepted the IETF academic standard for potential system architecture. For example, Moceri proposes that route optimisation (RO) would serve to eliminate inefficiency in tunnelling packets from MRs to their HA before being send to CNs over the internet. Essentially, this revised protocol would allow for MRs to send packets directly to CNs by sending binding updates with current CoAs to their CNs as they change attachment points. In spite of such optimisation strategies, Moceri suggests that there are several deficiencies in this reformation of the NEMO network architecture which could include increased signalling overhead, a longer handover delay, and the need to make devices such as CNs and MMNs aware of NEMO. A similar perspective is offered by Huang et al. who suggest that by establishing a packet forwarding control scheme, the triangular problem associated with PAR and NAR connections can be subverted. Although the Autonet router technology is patented and protected, it is likely that within this architecture a very similar vision of intra-nodal preparation and communication has been developed. Considering the widespread success of this technology, it can be confirmed that a forwarding control scheme is an optimal means of reducing handover latency and redundancy. Each of the academic theories integrated into the data presentation has focused on the implementation of a soft handover between multiple access points throughout a widely distributed network architecture. Given the handover challenge in mobile interfacing, the Chen et al. solution of multiple network types and multiple ISPs is one means of circumventing dropped connection syndrome and maintaining a more constant attachment to the HN. Although such schemes are complex, the value of a flexible, soft handover architecture is innately validated, suggesting that emergent technologies should avoid more static one-dimensional router architecture in order to improve upon handover and connection consistency. As Yang et al. demonstrated with their flexible WiMAX and WiFi network standard, the increase in choices regarding the bandwidth and quality of a particular access point will greatly reduce overall resource use and limit the network taxation associated with handovers. What is most important in such heterogeneous network architecture is that this technology is emergent at this stage and not widely appropriated across national and international networks. As bandwidth demands increase and the number of consumers engaging in mobile internet accelerates rapidly, the ability to dynamically manage exchange and handover protocol will be essential to the smooth and consistent functioning of internet access and communication. The new Autonet technology is designed to enhance portability even more by providing a singular router with a unique subscription that can be moved via docking station from vehicle to vehicle. Although this evolution could be considered yet another complication in an already challenging mobile router market, it is ultimately indicative of a commitment to dynamic, flexible architecture that is user-oriented and user-defined. This being said, in spite of limited technological sharing with the exception of an indication that the routing service runs on both 3G and 2.5G cellular data networks, it is evident that the network architecture for Autonet will grow increasingly complex in the near future. The findings of this academic review have indicated that a WiMAX protocol is being accepted by such agencies as the IETF as a means of achieving improved seamlessness in handover protocol in the future. As NEMO evolves and begins to integrate more complex pre-emptive packet sharing, the breadth of router sensing will ultimately determine how efficient this network runs. Therefore, by expanding this breadth through leading connectivity technology (WiMAX) that includes rapid speeds and a large coverage area, the more intrinsic conditions associated with this network architecture are likely to be more easily facilitated. Autonet, a leading firm in this industry, must continue to consider such advanced technologies, and although it maintains exclusivity with such automakers as Chrysler and Subaru, these features are optional, not universal, thereby restricting the user base to interested individuals. 5.3 Summary This chapter has introduced several of the concepts identified during the review of the empirical and theoretical studies, demonstrating the precedence which NEMO and WiMAX architecture continue to establish for future mobile router foundations. Undeniably, the ability to improve handover efficiency will prove invaluable as more individuals begin to join the vehicular internet community. For providers, such efficiencies equate to lower bandwidth consumption and improved efficiency, highly valuable considerations that should be discussed in great detail. The following and final chapter presents synthesis of the entirety of the data collected and analysed over this process.
Chapter 6: Conclusions and Recommendations
5.4 Conclusions From its Cadillac branding in some models to the unassuming black box in the trunk of the travelling salesman's car, the introduction of mobile internet routers into modern vehicles is a radical and increasingly popular concept. The costs are high from a product and a service perspective; however, given the bandwidth challenges associated with 3G and 4G service provision through mobile broadband cards and phones, the need for more dedicated mobile internet services is undeniable. The opportunities for firms such as Autonet are directly linked to consumer buy-in, an unpredictable standard that is directly associated with value for money and functionality concerns. From industry critics to general consumer resistance, overcoming deficiencies in performance and efficiency are likely to provide areas of opportunity to maximise price and improve market positioning. This investigation has explored six distinct research studies that have focused on one of the key segments of the mobile routing process, the handover phase. Considering the motion-oriented standard of the automobile, if handover is to be seamless, there must be some form of forecasting at work. For academics such as Huang et al., packet forwarding is simply essential in the introduction of a soft handover framework, as such technologies as WiMAX can be optimised in order to provide the largest breadth of connectivity possible. Further, as academics such as Kim and Koh have already shown what problems packet reordering can have on the functionality of a given network, it is becoming increasingly essential to consider more dynamic packet management in order to optimise network architecture and improve overall performance. Ultimately, the handover phase is incredibly uncertain, and given the advanced technologies that are continuing to emerge within this industry, it is likely that the future will hold even more radical evolutions of this technology. The authors in this research certainly believe that there is a precedence and a demand for more advanced technologies and in particular, more advanced handover practices. Therefore, instead of more restrictive, highly variable hard handovers, more flexible, efficiency-driven standards should become the future protocol. The findings in this investigation suggest that there is conflict within the interpretation that researchers have with the multiple theories that are emerging in this marketplace. For this reason, organisations such as the IETF need to advance their standardisation of this protocol, prescribing specific architecture, protocol, and technological foundations for future mobile internet applications. The evidence offered has demonstrated a broad spectrum of translatable theories and empirical findings; however, they are inconsistent. The practical application of this technology in the form of a consumer product is minimal, and with firms like Autonet available for testing, it is evident that more creative and innovative concepts are ready to be considered. The future of mobile internet suites are likely to radically alter the face of transportation, as traffic routing, inter-vehicular communication, and broadcast warnings are all likely to be controlled by the standard architecture of this technology. Ultimately, with even more fast paced conditions rising, it is essential that handover protocol is prioritised, and through the prescription of these multiple standards, the ability to improve beyond systemic and conceptual limitations is likely to be achieved. 5.5 Recommendations This research began with a singular product that has emerged out of a rich technological history to quickly become an OEM supplier to several large automotive retailers. Although the growth rate in annual sales between 2007 and 2010 was not significant considering the number of cars produced between those years, it is evident that the role played by Autonet in their optional application of router technologies is an essential one. The new CarFi system is unique and provides the flexibility needed to get many families and professionals excited about it. In a world that is characterised by additional fees add-on upgrades, to offer a single rate programme with router switching potential is an exemplary position for Autonet to take. Recognising that technology and capabilities are evolving, the following is a brief list of recommendations for this firm and other competitors seeking to enter into the mobile internet provider field:
- Enhance the Protocol and Architecture: Driven by the inefficiencies and fragmentation of the 3G protocol, Autonet must consider upgrading its standards to the WiMAX network. By expanding the scope of accessibility beyond existing limitations, significant consumption reduction can be achieved. By limiting the resources extracted via network connections and handover protocol, the bandwidth available for multimedia and various other applications will be maximised.
- Develop Portability: If automotive protocol is the wave of the future, then consideration should also be given to the maximisation of the past by allowing these router technologies to migrate into the household. In spite of the radically faster gains offered by WLAN and LAN technologies, by allowing these routers to transcend mobile and static lines, more consumers might consider this technology as a replacement for existing routers that cannot transition from house to car.
- Partner with Public Services: Focusing on infrastructure applications, the multi-node sensor and wirelessly connected internet control modules that have been predicted for future transportation management should be considered as viable and opportune technologies. Maximising these partnerships will ultimately enable a much broader spectrum of subscribers and participants, whereby firms will be able to begin to develop large scale coordination formats for their technology.
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Appendix A: Glossary of Key Technical Terms
- BS: Base Stations
- BSP: Basic Support Protocol
- CAP: Common Access Point
- CDMA: Code Division Multiple Access
- CN: Central Node
- D&M: Duplication and Merging
- FPHO: Fast Predicted Handover
- GPRS: General Packet Radio Services
- GPS: Global Positioning Satellite
- IETF: Internet Engineering Task Force
- IVCs: Inter Vehicle Communications
- MAC: Media Access Control
- MSCTP: Mobile Stream Control Transmission Protocol
- NAR: New Access Router
- NEMO: Network Mobility
- PAR: Past Access Router
- PFC: Packet Forwarding Control
- QoS: Quality of Service
- RO: Route Optimisation
- SIP: Session Initiated Protocol
- WiFi: Wireless Fidelity
- WLAN: Wireless Local Area Network
- WiMAX: Wireless Worldwide Interoperability for Microwave Access
- WPAN: Wireless Personal Access Network