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Dynamic Power Allocation and Routing for Time Varying Wireless Networks
 IEEE Journal on Selected Areas in Communications
, 2003
"... We consider dynamic routing and power allocation for a wireless network with time varying channels. The network consists of power constrained nodes which transmit over wireless links with adaptive transmission rates. Packets randomly enter the system at each node and wait in output queues to be tran ..."
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Cited by 211 (50 self)
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We consider dynamic routing and power allocation for a wireless network with time varying channels. The network consists of power constrained nodes which transmit over wireless links with adaptive transmission rates. Packets randomly enter the system at each node and wait in output queues to be transmitted through the network to their destinations. We establish the capacity region of all rate matrices (# ij ) that the system can stably supportwhere (# ij ) represents the rate of traffic originating at node i and destined for node j. A joint routing and power allocation policy is developed which stabilizes the system and provides bounded average delay guarantees whenever the input rates are within this capacity region. Such performance holds for general arrival and channel state processes, even if these processes are unknown to the network controller. We then apply this control algorithm to an adhoc wireless network where channel variations are due to user mobility, and compare its performance with the GrossglauserTse relay model developed in [13].
Power Allocation and Routing in Multibeam Satellites With TimeVarying Channels
 IEEE TRANSACTIONS ON NETWORKING
, 2003
"... We consider power and server allocation in a multibeam satellite downlink which transmits data to different ground locations over timevarying channels. Packets destined for each ground location are stored in separate queues and the server rate for each queue depends on the power ( ) allocated to th ..."
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Cited by 69 (18 self)
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We consider power and server allocation in a multibeam satellite downlink which transmits data to different ground locations over timevarying channels. Packets destined for each ground location are stored in separate queues and the server rate for each queue depends on the power ( ) allocated to that server and the channel state ( ) according to a concave ratepower curve ( ). We establish the capacity region of all arrival rate vectors ( 1 ... ) which admit a stabilizable system. We then develop a powerallocation policy which stabilizes the system whenever the rate vector lies within the capacity region. Such stability is guaranteed even if the channel model and the specific arrival rates are unknown. Furthermore, the algorithm is shown to be robust to arbitrary variations in the input rates and a bound on average delay is established. As a special case, this analysis verifies stability and provides a performance bound for the Choosethe LargestConnectedQueues policy when channels can be in one of two states (ON or OFF) and servers are allocated at every timestep ( ). These results are extended to treat a joint problem of routing and power allocation in a system with multiple users and satellites and a throughput maximizing algorithm for this joint problem is constructed. Finally, we address the issue of interchannel interference and develop a modified policy when power vectors are constrained to feasible activation sets. Our analysis and problem formulation is also applicable to power control for wireless systems.
Order optimal delay for opportunistic scheduling in multiuser wireless uplinks and downlinks
 Proc. of Allerton Conf. on Communication, Control, and Computing (invited paper
, 2006
"... Abstract — We consider a onehop wireless network with independent time varying channels and N users, such as a multiuser uplink or downlink. We first show that general classes of scheduling algorithms that do not consider queue backlog necessarily incur average delay that grows at least linearly wi ..."
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Cited by 28 (6 self)
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Abstract — We consider a onehop wireless network with independent time varying channels and N users, such as a multiuser uplink or downlink. We first show that general classes of scheduling algorithms that do not consider queue backlog necessarily incur average delay that grows at least linearly with N. We then construct a dynamic queuelength aware algorithm that stabilizes the system and achieves an average delay that is independent of N. This is the first analytical demonstration that O(1) delay is achievable in such a multiuser wireless setting. The delay bounds are achieved via a technique of queue grouping together with basic Lyapunov stability and statistical multiplexing concepts.
Logarithmic delay for N × N packet switches under the crossbar constraint
 IEEE Transactions on Networking
, 2007
"... Abstract—We consider the fundamental delay bounds for scheduling packets in an N ×N packet switch operating under the crossbar constraint. Algorithms that make scheduling decisions without considering queue backlog are shown to incur an average delay of at least O(N). We then prove that O(log(N)) de ..."
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Cited by 6 (0 self)
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Abstract—We consider the fundamental delay bounds for scheduling packets in an N ×N packet switch operating under the crossbar constraint. Algorithms that make scheduling decisions without considering queue backlog are shown to incur an average delay of at least O(N). We then prove that O(log(N)) delay is achievable with a simple frame based algorithm that uses queue backlog information. This is the best known delay bound for packet switches, and is the first analytical proof that sublinear delay is achievable in a packet switch with random inputs. The algorithm can be implemented with O(N 1.5 log(N)) total operations per timeslot. Similar results for switches with speedup are provided, and complexity and delay tradeoffs are considered. Index Terms — stochastic queueing analysis, scheduling, optimal control I.
Logarithmic Delay for N × N Packet Switches
 IEEE WORKSHOP ON HIGH PERFORMANCE SWITCHING AND ROUTING — APRIL 2004
, 2004
"... We consider the fundamental delay bounds for scheduling packets in an N × N packet switch operating under the crossbar constraint. Algorithms that make scheduling decisions without considering queue backlog are shown to incur an average delay of at least O(N). We then prove that O(log(N)) delay is ..."
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Cited by 3 (2 self)
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We consider the fundamental delay bounds for scheduling packets in an N × N packet switch operating under the crossbar constraint. Algorithms that make scheduling decisions without considering queue backlog are shown to incur an average delay of at least O(N). We then prove that O(log(N)) delay is achievable with a simple frame based algorithm that uses queue backlog information. This is the best known delay bound for packet switches, and is the first analytical proof that sublinear delay is achievable in a packet switch with random inputs. The algorithm is shown to be implementable with very low complexity, requiring O(N 1.5 log(N)) total operations per timeslot.
Equivalent models for queueing analysis of determinstic service time tree networks,” IEEE Tran. Information Theory, to appear. applied probability. Yu Ying received her M.S.E.E and B.S.E.E. degrees from Tsinghua University
 University of Waterloo
, 1998
"... Abstract — In this paper we analyze feedforward tree networks of queues serving fixed length packets. Using sample path conservation properties and stochastic coupling techniques, we analyze these systems without making any assumptions about the nature of the underlying input processes. In the case ..."
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Cited by 1 (0 self)
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Abstract — In this paper we analyze feedforward tree networks of queues serving fixed length packets. Using sample path conservation properties and stochastic coupling techniques, we analyze these systems without making any assumptions about the nature of the underlying input processes. In the case when the server rate is the same for all queues, the exact packet occupancy distribution in any queue of a multistage network is obtained in terms of a reduced 2stage equivalent model. Simple and exact expressions for occupancy mean and variance are derived from this result, and the network is shown to exhibit a natural traffic smoothing property, where preliminary stages act to smooth or improve traffic for downstream nodes. In the case of heterogeneous server rates, a similar type of smoothing is demonstrated, and upper bounds on the backlog distribution are derived. These bounds hold for general input streams and are tighter than currently known bounds for leaky bucket and stochastically bounded bursty traffic. Index Terms — stochastic coupling, network calculus I.
Networks with Time Varying Channels
, 2003
"... Satellite and wireless networks operate over time varying channels that depend on attenuation conditions, power allocation decisions, and interchannel interference. In order to reliably integrate these systems into a high speed data network and meet the increasing demand for high throughput and low ..."
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Satellite and wireless networks operate over time varying channels that depend on attenuation conditions, power allocation decisions, and interchannel interference. In order to reliably integrate these systems into a high speed data network and meet the increasing demand for high throughput and low delay, it is necessary to develop efficient network layer strategies that fully utilize the physical layer capabilities of each network element. In this thesis, we develop the notion of network layer capacity and describe capacity achieving power allocation and routing algorithms for general networks with wireless links and adaptive transmission rates. Fundamental issues of delay, throughput optimality, fairness, implementation complexity, and robustness to time varying channel conditions and changing user demands are discussed. Analysis is performed at the packet level and fully considers the queueing dynamics in systems with arbitrary, potentially bursty, arrival processes. Applications of this research are examined for the specific cases of satellite networks
IEEE Transactions on Networking, Feb. 2003 Power Allocation and Routing in MultiBeam Satellites with Time Varying Channels
"... Abstract We consider power and server allocation in a multibeam satellite downlink which transmits data to N different ground locations over N timevarying channels. Packets destined for each ground location are stored in separate queues, and the server rate for each queue i depends on the power p ..."
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Abstract We consider power and server allocation in a multibeam satellite downlink which transmits data to N different ground locations over N timevarying channels. Packets destined for each ground location are stored in separate queues, and the server rate for each queue i depends on the power p i (t) allocated to that server and the channel state c i (t) according to a concave ratepower curve µ i (p i, c i). We establish the capacity region of all arrival rate vectors (λ 1,...,λ N) which admit a stabilizable system. We then develop a power allocation policy which stabilizes the system whenever the rate vector lies within the capacity region. Such stability is guaranteed even if the channel model and the specific arrival rates are unknown. Furthermore, the algorithm is shown to be robust to arbitrary variations in the input rates, and a bound on average delay is established. As a special case, this analysis verifies stability and provides a performance bound for the “ChoosetheKLargestConnectedQueues” policy when channels can be in one of two states (ON or OFF) and K servers are allocated at every timestep (K<N). These results are extended to treat a joint problem of routing and power allocation in a system with multiple users and satellites, and a throughput maximizing algorithm for this joint problem is constructed. Finally, we address the issue of interchannel interference, and develop a modified policy when power vectors are constrained to feasible activation sets. Our analysis and problem formulation is also applicable to power control for wireless systems. satellite with onboard output queues