Mobile Group - Air Interface Technologies

In CCSR there are several technologies that we are researching in relation to improving the data throughput and multiple user aspects of mobile communications.

Cooperative Communication

Cooperative communication is emerging radio technique whereby distributed wireless devices within a network can share their local resources to improve the network performance. This technique has received increasing interests for wireless networks that demand quality-of-services, energy efficiency, and low cost devices. At CCSR, this research covers a wide area that includes network information theory, distributed code and modulation, and distributed signal processing. Recent research activities on this topic are involved in many European and EPSRC funded projects such as WINNER II and FIREWORKS under the framework of FP6, WHERE and ROCKET under the framework of FP7, and MVCE Efficiency Programme. Many original contributions have been made at CCSR, for example integrated routing and radio resource allocation, suboptimum resource-allocation strategies for OFDM-based cooperative relay network, advanced modulation and coding for cooperative communications, new cooperative strategies, novel robust receiver algorithms, analysis and design of new hybrid ARQ protocols, hybrid forwarding techniques, overlay cognitive radio techniques, etc.

Fundamental Capacity Limit

Finding an ultimate limit that any wireless cellular system with all advanced and smart transmission/reception and radio resource management techniques cannot exceed is very valuable and is a good indicative of the current optimisation status of the wireless communication systems. A research team under the umbrella of an elective program of mobile VCE, has been looking into this problem. The approach is based on global multi-cell processing concept (also known as global base station cooperation). Taking this approach, the fundamental capacity limits have been analytically derived for different realistic propagation conditions, sectorisation, multiple antenna, and cell density. Further focus will be on development of practical remedies to approach the predicted capacity limits. These remedies will include clustering, power control, resource (time/frequency/space) planning, and also inclusion of efficient wideband multiple access concepts.

Multicarrier Systems

OFDM turns out to be a very promising technique for high-data-rate communication systems. Many OFDM-based multiple access schemes such as SC-FDMA, OFDMA, MC-CDMA have already been the key air-interfaces for beyond 3G mobile communication systems. Towards the optimum combination of OFDM with other air-interface techniques, European commission has organised many research projects such as MATRICES, 4MORE, WINNER I/II, FIREWORKS, where CCSR is one of the key players. At CCSR, research activities towards OFDM are mainly in new air-interface design, robust synchronisation and channel estimation, optimum power allocation, heuristic joint subcarrier, bit, and power allocation, multiuser detection, etc. Many innovative techniques, such as hidden-pilot assisted MC-CDMA, LDS-OFDM, advanced iterative graph based decoding algorithms, optimum pilot design, novel synchronisation approaches, have been invented and published in many world-class journals and conferences.