Sudheer A. Grandhi

Centralized power control in cellular radio systems

This paper describes a centralized power control scheme for cellular mobile radio systems. The power for the mobiles in the proposed scheme is computed based on signal strength measurements. All the mobiles using the same channel in this scheme will attain a common carrier-to-interference ratio. The proposed scheme is analyzed and shown to have an optimal solution. >

Constrained power control

High system capacities can be achieved by controlling the transmitter power in multiuser radio systems. Power control with no constraint on the maximum power level has been studied extensively in earlier work [1–18]. Transmitter power is at a premium in radio systems such as cellular systems and PCS. There is a limit on the maximum transmitter power especially at the terminals (e.g. mobile units and handsets) since the power comes from a battery. In this paper we study power control that maximizes the minimum carrier to interference ratio (CIR), with a constraint on the maximum power. The optimal power vector solution lies on the boundary of the constrained power vector set and achieves a balance in the CIRs. Results indicate that the constraints do not induce any stability problems. A distributed scheme with favourable convergence properties and close to optimum performance is presented. Simulation results show that the algorithm tries to maximize the number of terminals served with CIR greater than or equal to the target CIR, while conserving power.

Distributed power control in cellular radio systems

The capacity of cellular mobile radio systems can be increased by controlling the transmitter powers so as to balance the carrier to interference ratios at the receivers. A distributed algorithm for implementing such power control was proposed earlier for satellite systems by Meyerhoff (1974). The authors tighten the mathematical arguments and apply this scheme to cellular systems. The mobile units adjust their transmitter powers at discrete time instants. Specifically at each time instant the mobile multiplies its current power by a factor equal to a constant over its current carrier to interference ratio (CIR). So power is increased or decreased based on the value of the current CIR. After a number of such power adjustments all the mobiles converge to a common CIR. They also present numerical results which show that the above scheme has the potential to converge faster than the scheme proposed by J. Zander (see IEEE Transactions on Vehicular Technology, vol.41, no.3, August 1992) for high CIR values. >

Constrained power control in cellular radio systems

High system capacities can be achieved by controlling the transmitter power in multiuser radio systems. Power control with no constraint on the maximum power level has been studied extensively in earlier work. Transmitter power is at a premium in radio systems such as cellular systems and PCS. There is a limit on the maximum transmitter power especially at the terminals (e.g. mobile units and handsets) since the power comes from a battery. In this paper we study power control that maximizes the minimum carrier to interference ratio (CIR), with a constraint on the maximum power. The optimal power vector solution lies on the boundary of the constrained power vector set and achieves a balance in the CIRs. Results indicate that the constraints do not induce any stability problems. A distributed scheme with favourable convergence properties and close to optimum performance is presented. Simulation results show that the algorithm tries to maximize the number of terminals served with CIR greater than or equal to the target CIR, while conserving power.<<ETX>>

Distributed dynamic channel assignment schemes

Some distributed channel schemes for a one-dimensional cellular radio system are described. The channel assignment in the schemes proposed is based on signal strength measurements and therefore gives an improvement in capacity over schemes using reuse distance criterion for channel assignment. The proposed schemes are evaluated by simulations and their behavior with variation in traffic density, size of the channel set and number of reassignments is studied.

Simulation of self-organizing spectrum management in wireless networks

We describe the simulation of a new dynamic channel assignment algorithm in FDMA/TDMA wireless networks. The algorithm relies on periodic interference measurements by each of the base stations on the inactive frequencies, so as to identify appropriate candidate channels. The adaptive nature provides automatic configuration at the time of system initialization and adaptation to system expansion and traffic patterns with spatial or temporal variations. By eliminating the manual frequency planning process inherent to todays fixed channel assignment procedures, the self-organizing capability guarantees ease of operation for service providers, while increasing both capacity and voice quality. Our simulation experiments demonstrate stability of the algorithm and confirm its self-organizing capability. They also indicate a significant decrease of call blocking and dropping and other quality-of-service improvements.