Shou C. Chen

Bio: Shou C. Chen is an academic researcher from University of California, Los Angeles. The author has contributed to research in topics: Power control & Wireless network. The author has an hindex of 5, co-authored 6 publications receiving 677 citations.

Channel access algorithms with active link protection for wireless communication networks with power control

Abstract: A distributed power-control algorithm with active link protection (DPC/ALP) is studied in this paper. It maintains the quality of service of operational (active) links above given thresholds at all times (link quality protection). As network congestion builds up, established links sustain their quality, while incoming ones may be blocked and rejected. A suite of admission control algorithms, based on the DPC/ALP one, is also studied. They are distributed/autonomous and operate using local interference measurements. A primarily networking approach to power control is taken here, based on the concept of active link protection, which naturally supports the implementation of admission control. Extensive simulation experiments are used to explore the network dynamics and investigate basic operational effects/tradeoffs related to system performance.

Radio link admission algorithms for wireless networks with power control and active link quality protection

Abstract: Presents a distributed power control scheme, which maintains the signal/interference ratios (SIRs) of operational (active) links above their required thresholds at all times (link quality protection), while new users are being admitted; furthermore, when new users cannot be successfully admitted, existing ones do not suffer fluctuations of their SIRs below their required thresholds values. The authors also present two admission/rejection control algorithms, which exercise voluntary drop-out of links inadmissible to the network so as to reduce interference and possibly facilitate the admission of other links.

Admission control schemes for wireless communication networks with adjustable transmitter powers

Abstract: When new mobiles are admitted in some channel of a wireless communication network traditional power control algorithms cannot foresee the effect that new admissions have on the signal-to-interference ratios (SIR) of active mobiles already using the channel, and may cause fluctuations of their SIR below acceptable levels during the process. The authors present two algorithms that manage transmission power and channel admissions jointly to maintain the SIR of all links above some quality factor /spl gamma/ at all times. This joint control of power and channels results in high channel reuse. >

On distributed power control for radio networks

Abstract: Due to co-channel interference, the carrier to interference ratios (C/I) of some mobiles in a wireless network may drop below a desired quality threshold /spl gamma/, either upon admission of a new mobile or if channel conditions vary. By using dynamic, local measurement of the power gains between base stations and mobiles, we develop a new distributed algorithm for power control which operates by adjusting the transmitted powers from the base stations so as to maintain the C/I of every link above the desired threshold. >

A distributed, mobile wireless infrastructure for multimedia applications

Abstract: A distributed, mobile network infrastructure for wireless multimedia applications is presented. This network is not constrained by a fixed backbone network as conventional cellular systems are. By using a clustering algorithm, nodes are organized into clusters. The access scheme relies on both time/code division inside a cluster and code separation across clusters. Clustering enhances the spatial reuse of time slots and codes. A TDMA structure provides bandwidth guarantee for real time traffic. Using different codes for different clusters by appropriate power control algorithms can increase the channel capacity. A fast reservation virtual circuit scheme allows us to extend the bandwidth guarantee also to mobile environments. Simulation experiments evaluate the performance of the proposed scheme.

The capacity of wireless networks

Abstract: When n identical randomly located nodes, each capable of transmitting at W bits per second and using a fixed range, form a wireless network, the throughput /spl lambda/(n) obtainable by each node for a randomly chosen destination is /spl Theta/(W//spl radic/(nlogn)) bits per second under a noninterference protocol. If the nodes are optimally placed in a disk of unit area, traffic patterns are optimally assigned, and each transmission's range is optimally chosen, the bit-distance product that can be transported by the network per second is /spl Theta/(W/spl radic/An) bit-meters per second. Thus even under optimal circumstances, the throughput is only /spl Theta/(W//spl radic/n) bits per second for each node for a destination nonvanishingly far away. Similar results also hold under an alternate physical model where a required signal-to-interference ratio is specified for successful receptions. Fundamentally, it is the need for every node all over the domain to share whatever portion of the channel it is utilizing with nodes in its local neighborhood that is the reason for the constriction in capacity. Splitting the channel into several subchannels does not change any of the results. Some implications may be worth considering by designers. Since the throughput furnished to each user diminishes to zero as the number of users is increased, perhaps networks connecting smaller numbers of users, or featuring connections mostly with nearby neighbors, may be more likely to be find acceptance.

On the capacity of a cellular CDMA system

Abstract: It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

A framework for uplink power control in cellular radio systems

Abstract: In cellular wireless communication systems, transmitted power is regulated to provide each user an acceptable connection by limiting the interference caused by other users. Several models have been considered including: (1) fixed base station assignment where the assignment of users to base stations is fixed, (2) minimum power assignment where a user is iteratively assigned to the base station at which its signal to interference ratio is highest, and (3) diversity reception where a user's signal is combined from several or perhaps all base stations. For the above models, the uplink power control problem can be reduced to finding a vector p of users' transmitter powers satisfying p/spl ges/I(p) where the jth constraint p/sub j//spl ges/I/sub j/(p) describes the interference that user j must overcome to achieve an acceptable connection. This work unifies results found for these systems by identifying common properties of the interference constraints. It is also shown that systems in which transmitter powers are subject to maximum power limitations share these common properties. These properties permit a general proof of the synchronous and totally asynchronous convergence of the iteration p(t+1)=I(p(t)) to a unique fixed point at which total transmitted power is minimized. >

Adaptive clustering for mobile wireless networks

Abstract: This paper describes a self-organizing, multihop, mobile radio network which relies on a code-division access scheme for multimedia support. In the proposed network architecture, nodes are organized into nonoverlapping clusters. The clusters are independently controlled, and are dynamically reconfigured as the nodes move. This network architecture has three main advantages. First, it provides spatial reuse of the bandwidth due to node clustering. Second, bandwidth can be shared or reserved in a controlled fashion in each cluster. Finally, the cluster algorithm is robust in the face of topological changes caused by node motion, node failure, and node insertion/removal. Simulation shows that this architecture provides an efficient, stable infrastructure for the integration of different types of traffic in a dynamic radio network.