The sum-rate capacity of a cellular system model is analyzed, considering the uplink and downlink channels, while addressing both nonfading and flat-fading channels. The focus is on a simple Wyner-like multicell model, where the system cells are arranged on a circle, and the cell sites are located at the boundaries of the cells. For the uplink channel, analytical expressions of the sum-rate capacities are derived for intra-cell time-division multiple-access (TDMA) scheduling, and a "wideband" (WB) scheme (where all users are active simultaneously utilizing all bandwidths for coding). Assuming individual equal per-cell power constraints, and using the Lagrangian uplink-downlink duality principle, an analytical expression for the sum-rate capacity of the downlink channel is derived for nonfading channels, and shown to coincide with the corresponding uplink result. Introducing flat-fading, lower and upper bounds on the average per-cell ergodic sum-rate capacity are derived. The bounds exhibit an O(loge Κ) multiuser diversity factor for a number of users per cell Κ ≫ 1, in addition to the array diversity gain. Joint multicell processing is shown to eliminate out-of-cell interference, which is traditionally considered to be a limiting factor in high-rate reliable communications.
Bibliographical noteFunding Information:
Manuscript received August 19, 2005; revised August 15, 2007. This work was supported by the REMON Consortium, Israel Ministry of Commerce. The material in this paper was presented in part at the 9th Canadian Workshop on Information Theory (CWIT), Montréal, QC, Canada June 2005, and at the 3rd International Workshop on Signal Processing for Wireless Communications (SPWC 2005), London, U.K., June 2005.
- Distributed antenna array
- Multicell processing
- Multiuser detection
- Multiuser diversity
- Shannon theory
- Wyner's cellular model