RESEARCH REQUIRED FOR 4G WIRELESS APPLICATIONS

The common research areas which are evolving for 4G of wireless communication systems are:

1. New decoding algorithms for turbo codes for wireless channels.
2. New coding/modulation techniques for reducing the peak-to-mean envelope ratio, maximizing the data rate and providing large coding gain.
3. New approaches to jointly designing modulation techniques, and power amplifiers to simultaneously obtain high power added efficiency along with bandwidth efficiency.
4. New demodulation / decoding techniques to simultaneously combat the near-far problem and do channel decoding in multi-rate DS-CDMA (Direct Sequence Code Division Multiple Access) systems.
5. Communication problems unique to high frequency systems (e.g., channel estimation).
6. Joint channel estimation and decoding/demodulation algorithms.
7. Multiple-access techniques for multi-rate systems with variable quality of service requirements.
8. Space-time coding for systems with multiple antennas.
9. Analog decoding techniques for high speed, low power systems.
10. Ultra wideband systems and hardware design. (xi) Research in methodologies for an integrated approach to wireless communications (device layer: e.g., power and low noise amplifiers, mixers, filters; physical layer: coding, modulation; medium access layer: CDMA/FDMA/TDMA; data link layer: hybrid ARQ (Automatic Repeat Request); network layer: routing protocols).

CURRENT RESEARCH FOR MOBILITY MANAGEMENT IN 4G

There is considerable research being done on mobility management. Mobility solutions can be found by either developing improvements within the current architecture, or by revising the architecture to reflect the changing environment. The solutions propose different addressing and packet forwarding schemes. Almost all of them are IP based solutions, which allow interoperability and easy integration with the existing architectures. Within each of the solutions the relevance to mobility and their strengths and limitations, are discussed in brief:

1. The Internet Indirection Infrastructure is a scalable, self-organizing scheme which easily integrates with legacy systems. It proposes an architecture that offers a communication abstraction based on rendezvous points in an overlay network. When a host wants to send a packet, it forwards the packet to one of the servers it knows. A packet keeps traversing the network till the target server is reached; this leads to delay in route discovery and packet forwarding.
2. FARA (Forwarding directive, Association, and Rendezvous Architecture) is an ongoing project whose main purpose is to provide mobility by separating location from identity. One advantage is that neither an entirely new namespace nor a globally unique one is required for the entities. It allows several different forwarding mechanisms to co-exist in the network, resulting in variability in characteristics like mobility, identity, and anonymity. However, FARA model fails to take into consideration many packet forwarding issues like performance of network nodes, or the balance of anonymity vs. identity for communicating endnodes. It does not accommodate for security either.
3. Host Identity Payload (HIP) provides another way of breaking the binding between identities and topological locations of network nodes. HIP introduces new cryptographic identities that can be dynamically mapped to IP addresses. However, HIP Host Identity (HI). being a public key, is not practical in all actions; it is somewhat long, it needs to be hashed before being used in IPv6 applications. While providing support for mobility and multi-homing with a major architectural change in the addressing concept, the solution requires only small changes in current host implementations.
4. IST MIND develops the concepts and protocols generated in BRAIN by enabling hosts to cooperate with self-organizing wireless ad-hoc networks. It provides independent, interoperable solutions for local/micro-mobility from global mobility.
5. DRIVE specifies a multi-access architecture allowing for seamless intersystem- handover. The concept of a host-controlled flow control was developed to enable parallel usage of different access systems. The architecture is based on Hierarchical Mobile IP, extended by an AAA (Authentication, Authorization and Accounting) component. Over DRiVE extends the scenario with moving networks (e.g. vehicles, trains, etc.) in a multiradio/multi-access environment, defines a Mobile IP-based solution, and focuses on multicast support. The project has strong influence on the ongoing work within the IETF NEMO (Network Mobility) group.
6. The Architectural Principles of Ambient Networks require the integration of a multitude of different communication environments, rather than suffering from heterogeneity. The approach is to use network composition as the principle instead of terminals; networks as such can form the basic building block of the communication architecture. Network composition is a more powerful concept than the simple internetworking as enabled by the Internet Protocol. The current Internet assumes homogeneity in the environment in which to provide control. Ambient Networks have the potential to solve this issue of fragmented control.
7. Developing Standards for Seamless & Secure Mobility: Several industry consortia and standard development organizations such as the IEEE 802 LAN/MAN Standards Committee and the Internet Engineering Task Force (IETF) are expending considerable efforts to develop a common framework and extend existing mobility protocols in order to facilitate and optimize handover performance. Various activities are currently under way, including extensions to Mobile IP at the IETF, and the formation of the Media Independent Handover (MIH) working group in IEEE 802, in addition to several task groups within IEEE 802.11 in order to deal with roaming (IEEE 802. 11r) and interfacing to external networks (IEEE 802.11u) .
8. Interference Alignment Techniques for Wireless Interference Channels: The project is going at Samsung Advanced Institute of Technology, Korea from Nov. 2008 onwards.
9. Transmission Techniques for Multiple MIMO Relay Channels: This project is being developed at LG Electronics, Korea from Aug. 2008.
10. Physical Layer Design for High-speed wireless Systems (9^th): The project is going at Interstate Technology & Regulatory Council.

The best solution among the current and ongoing projects will be the one that successfully addresses all the related challenges as well as allows scalability for future possibilities. A few open issues, however, need to be addressed in most of the existing projects; i.e. synchronization of the entire network and sound QoS.

FUTURE RESEARCH DIRECTIONS

The following directions are envisaged for future research. There is much research potential in the new fields of (i) third-party authentication, authorization, and accounting (3P-AAA) and third-party charging and billing (3P-C&B) and (ii) WBCs and ADA. Some ideas and directions are listed in the following. Included also is a suggestion to develop a cross-layer reference communications model to aid in design and analysis of open cross-layer functionalities.

3P-AAA and 3P-C&B

• Extending 3P-AAA into the area of wireless Ad Hoc networks. This can yield significant 3P-AAA use cases influencing the 3P-C&B requirements. Typical Ad Hoc domain scenarios involving hot-zone wireless heterogeneous architectures are envisaged where mobile terminals use multi-hop techniques to get to a hot zone using intermediate mobile terminals (the latter should benefit from their role in such scenarios, i.e., be paid properly).
• Research to date has identified and established the basic charging scenarios in CBM-based UCWW by employing inter-3P-AAA-SP signalling. However, when the inter-3P-AAA-SP signalling involves Internet usage, then charging interactions can experience high network latency. To eliminate this problem either further optimization is needed in the 3P-AAA-SP signalling (i.e., compressing the messages where possible) or a new ‘charging agent’ concept should be developed. This new concept would result in the following: (1) the charging occurs in the metering domain (TSP/ANP), (2) the charging agent is downloaded from the 3P-AAA-SP to provide the charging function in the TSP/ANP domain, (3) the charging agent imports the charging rule set from the 3P-AAA-SP, (4) the charging agent imports segments of the consumer account into the metering domain.
• Elaboration of the C&B framework to support dynamic reconfiguration of applicable metering and pricing policies for specific service, specific user or combination of both, and to support various pricing models according to the service profile, user profile and location, and one-stop billing schemes.
• Implementation of a C&B system prototype as a discrete service that can be provided by a trusted third-party authentication, authorization and accounting service providers (3P-AAA-SPs).
• Running trial experiments with the designed prototype in a 4G testbed environment showing good interfacing with the 3P-AAA service, WBC&ADA services, and other (new) types of 4G services (e.g., consumer-oriented ICC service).

WBC and ADA

• At the WBC Service Layer - Besides the intelligent software architecture already mentioned, other issues for future investigation include:
• Agent environment: JADE has been used to date to act as an agent environment in the heterogeneous WBC software architecture. However, JADE is a heavy agent platform with a big footprint for executing both the SD collecting, clustering, scheduling, indexing, broadcasting on the server side, and the SD discovery and association on the mobile terminal side. In addition, it does not fully support the BDI agent. Therefore, investigation into lightweight BDI-based Java agent platforms (WBC-BDI) is recommended. Formatting the communication language's messages with WBC-ASN is also recommended, as well as ensuring that the agent platform functions correctly in the following environments: J2SE (Sun Java 2 platform, standard edition 2003), J2ME (Sun J2ME Specification 2009), Android (Google Android Software Development Kit 2008), WinCE (Windows Embedded CE Overview 2008), etc.
• SD formatting: In order to encode SDs in a more compact way, an efficient abstract syntax notation language based on ASN.1 (WBC-ASN) is suggested. Any design should take into account the requirement for minimizing decoder's power consumption.
• Rule engine: Resolution of the need to improve the flexibility and scalability could be approached by designing an intelligent SD self-organization lightweight Java rule engine. In suggesting this, we also recommend that the rules configuration file here could be defined with WBC-ASN.
• ADP: Designing with system scalability in mind, the route of developing the ADP protocol in Java, together with a Java-based Reed-Solomon algorithm being fully implemented is suggested as worthy of investigation.
• Profile design: To increase security and privacy for WBC-SPs, and mobility and personalization for mobile users, investigation of the benefits from this perspective of a well-structured rule-based profile developed and formatted with WBC-ASN is suggested.
• At the WBC Link Layer and Physical Layer - Potential broadcast platform solutions include WBC over DVB-H, over DRM, over DAB, etc. Investigations in the technical realization configurations for each have yet to be undertaken. There is little doubt about the potential consumer base into which WBC advertisement may be pushed. Today, for instance, there is an expectation of 300 million DVB-H capable handsets operational by 2009/10.

Cross-Layer Reference Communication Model

Some activities within UCWW, such as end-to-end (E2E) hot access network change (HAC) based on user-driven ABS&S policies, require cross-layer protocol functionality. Other examples include E2E reconfigurability (Z. Boufidis et. al., 2004, Sept), service adaptability (Houssos, N., et. al. 2003), E2E QoS support (Politis, C. al., 2004), ABC&S (O'Droma, M., Ganchev, I, et. al., 2006), user/network/service/terminal profile management, 3P-AAA and related 3P-C&B, and WBC & ADA operation. While this seems to contradict the layering architecture model for designing, planning, implementing and analysing communication protocols, nonetheless, it is the reality and it is worthwhile to structurally allow for it with suitable modifications of the reference models. Such a suitably modified reference communication model is presented in Figure 1. 

It has similarities with the B-ISDN/ATM reference communication model in that it is a 3D model consisting of three planes: user plane, control plane, and management plane. The new central element, which intersects all three planes, is added to allow for structured cross-layer functionality. This cross-layer core cylinder is a modification ofthat proposed in (Ganchev, I., O'Droma, M., et. al., 2006) and may be visualized as consisting of several parallel mini cylinders each with its own dedicated functionality, e.g., corresponding to the activities already listed above with cross-layer protocol functionality. Formal reflecting of these activities and their cross-layer functionalities into this model will assist their formal design and analysis, and facilitate development of formal and open primitives and APIs.

Figure 1: The proposed cross-layer reference communication model