The imminent commercial deployment of the 3rd generation 3rd wireless communications systems has placed the development of future high rate wireless internet and mobile computing at the top of wireless R&D agenda. Wireless channels are known to be unreliable and volatile. To develop even faster wireless data networks that can serve as the essential last link for both nomadic and highly mobile users, wireless system design may require fundamental changes in approach. To this end, it has been widely recognized that quality-of-serve (QoS) awareness should be introduced to lower network layers through a unified design. Even within the physical layer itself, separate function blocks such as transmit diversity, equalization, and coding must be further integrated to better exploit the available channel bandwidth, antenna diversity, and channel coding in order to compensate for unknown and time-varying channel distortions as well as co-channel interferences. This proposal presents a novel framework for the design integration and VLSI implementation of ARQ based wireless data networks and highlights a number of critical open research issues for investigation along with many highly promising solutions.
The proposed project centers on a unified approach to the design integration of ARQ, transmit/receiver diversity, equalization, and channel coding in broadband wireless communication systems. It represents a clear departure from the current transceiver (physical layer) design approach that separately determines and optimizes each individual functionality such as channel coding, coded modulation, and channel equalization. Central to the PIs proposal is the idea to exploit the use of QoS driven hybrid ARQ at both the transmitter and the receiver. This idea represents an important step of design integration based on the network use of hybrid ARQ. The PIs proposal focuses on a specific mechanism facilitated by an ARQ feedback channel to achieve design coordination of physical layer functions of channel equalization/pre-compensation, transmit antenna diversity, (turbo) coding, amid hybrid ARQ. Their proposed approach is very general and is not limited to a specific modulation or network standard. In particular, their research objectives amid tasks include
o Joint optimization of turbo coding, turbo equalization, amid multiuser detection through code awareness based on temporal diversity introduced by hybrid ARQ;
o Turbo equalization amid multiuser detection algorithms for transmit diversity with variable rate codes that are exploited by the transmitter amid demodulator;
o Broadband spatial turbo equalization combined with H-ARQ diversity utilizing codes of different levels of error protection as well as iteratively decodable multilevel codes;
o New type II hybrid ARQ based on integration of parity retransmission, concatenation, Reed-Solomon (RS) outer code, low-density parity check (LDPC) inner code, arid turbo coding.
o VLSI design amid implementation of high speed decoders for integrated equalization, LDPC, and RS turbo decoding.
o Low complexity two-stage turbo decoding of Reed-Solomon codes through their binary decomposition into binary component codes with relatively small state complexity;
Rather than pursuing incremental advances separately in diversity combining, H-ARQ, equalization, and coding, this project presents a new and specific network integration approach that will have a strong impact on the design of future wireless data networks. The VLSI design amid implementation will represent the latest technology for broadband high speed communication systems.
