Optimization of space time block codes on the downlink and energy efficiency on the uplink for CDMA wireless networks.

摘要

This thesis deals with two topics in wireless cellular communications: space-time block codes for the downlink channel and energy efficiency procedures for the uplink channel for CDMA wireless networks. Spectral efficiency on the downlink is a key system performance parameter. Differential space-time block codes (STBC) can provide the potential for an inexpensive implementation for both the encoder and decoder. A finite constellation allows large-range voltage multipliers to be replaced with lookup tables. Quaternion-based differential STBC with finite constellation are exhaustively described, and are used to propose a specific octahedral STBC (size 48), with a simple decoder composed of two symbol-wise decoders and a four-bit full constellation decoder. Simulations using the SUI (Stanford University Intermediary) Channel Model 3 show the new code's advantages (in terms of spectral efficiency or BER) over existing codes. Energy efficiency on the uplink can provide longer battery life to mobile devices and less user interference, which leads to higher user capacity.; A theoretical framework is derived for studying cooperative games in single base station CDMA networks. Cooperative strategies are described analytically and demonstrated numerically. The special cooperative case of maximal fairness is studied in depth and shown to benefit greatly from a cooperative framework using power control or power control and carrier selection strategies. For the basic case of power control, strategies are enhanced by allowing either carrier selection or rate control. For power control with carrier selection, numerical results again show the benefit of the cooperative framework over selfish optimization, as well as the benefits of using multiple carriers versus a single carrier. For power and rate cross-layer strategies, quality of service (QoS) goodput and delay constraints are studied analytically. Rate-constrained cross-layer joint optimization is shown to be achievable through a non-cooperative framework. Delay-constrained cooperative optimization is shown to offer little advantage over non-cooperative optimization for the particular packet transfer rate used. Finally, we show that power control games with users having either goodput or energy efficiency goals offer relevant insights into networks combining cooperative and non-cooperative users.