Joint link quality and power management over wireless networks with fairness constraint and space-time diversity
In multiaccess wireless networks, dynamic allocation of resource such as link qualities and transmitted powers is an important means to combat time-varying fading environments and cochannel interferences (CCIs). In most prior work, every link's quality is maintained by having a fixed signal-to-interference-noise-ratio (SINR) requirement. We discover that such a constraint is too strong and can degrade the performance of entire wireless networks, because a user with a bad channel response requires too much transmitted power and, therefore, causes unnecessary CCI to other users. In this paper, we alleviate this constraint and explore the time and multiuser diversity. For each user, the time-average link quality is maintained as a constant to ensure fairness. For the whole system, we want to minimize the overall transmitted power. In order to solve this problem, each user provides the system with a SINR range that is acceptable, according to the channel conditions and transmission history. Then, the system allocates the resources according to these ranges, channel conditions, and other practical constraints. Each time, some users may sacrifice their performances to reduce the overall network transmitted power. These users' temporary sacrifices will improve the system performance and will be paid back in the long term. This scheme can be conceived of as "water filling" the wireless network resources to different users at different times. In addition, by combining the proposed scheme with beamforming, we can have one more degree of freedom to combat CCIs in different directions of arrivals and different channel conditions over time.