An Uplink Proposal Based On Adaptive Interleave-Division Multiple Access

INTRODUCTION systems are expected to achieve the following goals: • Quality of service (QoS) provisioning Packet-based data services (probably using mobile IPv6) Parallel data streams with different QoS classes (supporting hierarchical source coding and video streaming, for example) Low delay • System scalability (w.r.t. data rates, bandwidth, cell sizes, etc.) High peak rates (about 100 Mbps for high mobility and 1 Gbps for low mobility or local wireless access) Scalable bandwidth (about 20 MHz to 100 MHz in 5 MHz slots) Variable cell sizes (incl. pico, micro, and macro cells) • High bandwidth efficiency (about 4-10 bits/s/Hz) and simultaneously high power efficiency • High-speed mobility, high velocities, fast adaptation • Low computational complexity (iterative processing). Efficient transmission techniques and cross-layer design and optimization techniques are required to implement these goals. Due to many factors, direct-sequence code-division multiple access (DS-CDMA) is currently an attractive candidate particularly for the uplink. DS-CDMA offers well-known features: Dynamic channel sharing, soft capacity, reuse factor of one, low drop-out rate and large coverage (due to soft handover), ease of cellular planning, robustness to channel impairments and immunity against interference, etc. These advantages are due to spreading the information over a large bandwidth (“wideband transmission”). IDMA can be considered as a special case of DS-CDMA. In IDMA, each data stream is first encoded by a (very) low-rate encoder. Conceptionally, the same encoder can be used for each data stream (i.e., even different users use the same encoder). For convenience, each data stream is referred to as a layer. We assume that the encoder is binary, hence the layers are binary as well. Subsequently the coded bits, usually referred to as chips in this context, are interleaved. The main difference between IDMA and DSCDMA is that in IDMA each layer is assigned a layer-specific interleaver, whereas in DSCDMA a layer-specific spreader is applied. As a consequence, in IDMA chip-by-chip interleaving is done and no spreading code is used. Finally, the encoded and interleaved data streams of different layers of the same user are linearly superimposed (preferably with different phases and amplitudes) before transmission. The data rate can be adapted by superimposing a variable number of layers. In contrast to other system designs, An Uplink Proposal Based On Adaptive Interleave-Division Multiple Access