Long Ke-ping

A Novel Random Backoff Algorithm to Enhance the Performance of IEEE 802.11 DCF

The Probability Distribution of Slot Selection (PDoSS) of IEEE 802.11 DCF is extremely uneven, which makes the packet collision probability very high. In this paper, we propose a novel RWBO+BEB backoff algorithm for 802.11 DCF to make the PDoSS even and thus decrease the packet collision probability. A Markov model is built for analyzing RWBO+BEB’s PDoSS and saturation throughput. The model’s correctness is validated by simulation. The performance of RWBO+BEB is also evaluated by simulation in terms of PDoSS, saturation throughput, packet collision probability and packet delay. The simulation results indicate that RWBO+BEB can decrease the packet collision probability to a large extent, utilize the channel more efficiently, and make the packet delay jitter much lower comparing to 802.11 DCF. Moreover, we analyze the relation of saturation throughput and packet collision probability to walking probability (pd ) and contention windows (w), respectively. The analysis indicates that RWBO+BEB has a remarkable feature: its saturation throughput keeps high, and packet collision probability keeps very low (which under 0.1) in a large range of pd and w, this allows us to configure pd and w more flexibly.

Effective fairness queuing algorithms

In this paper we present two effective fair queuing algorithms (EFQs), which achieves fairness properties and delay properties similar to WFQ (which is currently the better scheduling algorithm among others), and uses a system potential function of O(l) complexity. In EFQs, computation of system potential function does not require any division or multiplication operations such as in minimum delay-self clocked fair queuing (MD-SCFQ). Compared to MD-SCFQ, EFQs have lower complexity and can be easily implemented on chips. We verify the effectiveness of the proposed EFQs through theoretical analysis and give some simulation results.

Analyzing the delay performance of server-based and receiver-based local recovery approaches for reliable multicast

Local recovery approaches for reliable multicast can be classified into a server-based and receiver-based approaches. This paper presents a delay analysis of server-based (L1) and receiver-based (L2) local recovery approaches for reliable multicast. We focus on the average delay between the initial arrival of a packet at the sender and its correct reception at a randomly selected receiver. Our analysis shows the following characteristics. (1) Except for extremely low loss, L2 usually becomes saturated under lower arrival rates than L1. (2) When the tail links per repair server increases, the saturated value of L1 decreases. However, L1 is still better than L2 even if the tail links per repair server comes to 200. (3) The delay performance of L1 will hardly change if we increase the number of tail links and keep k constant. The delay performance of L1 is more scalable than that of L2.

A new synchronous digital hierarchical Bi-directional ring capacity design algorithm based on the shortest-route traffic matrix

In this paper, the concept of the Shortest-Route Traffic Matrix(SRTM) was first presented, and the generalized formula for computing ring capacity requirement in use of SRTM is given. Then, a new capacity design algorithm which is based on SRTM was presented for Synchronous Digital Hierarchical(SDH) Bi-directional Self-Healing Ring (BSHR). The algorithm simulation results demonstrate that this algorithm is very efficient for SDH BSHR capacity design and can make less project investment and make high utilization of lines and equipment. By means of the algorithm in this paper, capacity optimization assignment for SDH Hierarchical Self-Healing Ring (HSHR) and for ATM Virtual Path (VP)-based Self-Healing Ring (SHR) is also discussed.