Hints on writing technical papers and making presentations

An account is given on guidelines on writing good technical papers and making good presentations. The information given will help in effectively communicating ideas and results to the research community.published_or_final_versio

Interference estimation for admission control in multi-service DS-CDMA cellular systems

Wideband code division multiples access (CDMA) is one of the major options for the next generation mobile cellular system. However, there is only limited research on the admission control for CDMA systems containing multiple service classes. In this paper the multi-service CDMA admission control problem is addressed by an approach which is conceptually simple, and yet produces satisfactory results. In our approach the limit on the acceptable interference level in a cell is translated into a constraint on the number of users of each service class in the local and neighboring cells. The randomness of user locations, shadowing and imperfect power control is captured as a whole by a log-normal distribution. Simulation results show that this approach is quite accurate over a wide range of required system outage probabilities.published_or_final_versio

Generalized load sharing for packet-switching networks

In this paper, we propose a framework to study how to effectively perform load sharing in multipath communication networks. A generalized load sharing (GLS) model has been developed to conceptualize how traffic is split ideally on a set of active paths. A simple traffic splitting algorithm, called weighted fair routing (WFR), has been developed at two different granularity level, namely, the packet level, and the call level, to approximate GLS with the given routing weight vector. The packet-by-packet WFR (PWFR) mimics GLS by transmitting each packet as a whole, whereas the call-by-call WFR (CWFR) imitates GLS so that all packets belonging to a single flow are sent on the same path. We have developed some performance bounds for PWFR and found that PWFR is a deterministically fair traffic splitting algorithm. This attractive property is useful in the provision of service with guaranteed performance when multiple paths can be used simultaneously to transmit packets which belong to the same flow. Our simulation studies, based on a collection of Internet backbone traces, reveal that WFR outperforms two other traffic splitting algorithms, namely, generalized round robin routing (GRR), and probabilistic routing (PRR). These promising results form a basis for designing future adaptive constraint-based multipath routing protocols.published_or_final_versio

DIVeR: a dynamic interactive video retrieval protocol for disk array based servers

Video-on-demand (VOD) is a very promising multimedia application of the near future. In order for such a service to be commercially viable, efficient storage and retrieval schemes need to be designed. A scheme for grouping MPEG frames into segments wherein no frames are discarded during fast playback is proposed. In addition, the Dynamic Interactive Video Retrieval (DIVeR) protocol is introduced for scheduling the retrieval of multiple users from disk-array servers.published_or_final_versio

Decomposition of network of queues with self-similar traffic

Jackson's network of queues model greatly simplifies the performance analysis of telecommunication networks with Poisson traffic arrivals and exponential service times. It reduces the analysis of a network into the analysis of individual communication links, each of which may be modeled as an M/M/m queue. Motivated by the growing significance of self-similar traffic in modeling broadband network traffic, we propose a new network of queues model for telecommunication networks. Our model resembles Jackson's model except that the arrival is self-similar and the service time is deterministic. It captures the characteristics of modern high speed cell-based networks. We hypothesize a result analogous to Jackson's Theorem, that each mode of this network model behaves as a G/D/1 queue with self-similar arrival. Based on this hypothesis, many network-wide performance measures, such as the end-to-end delay, can be evaluated in a simple fashion. Our hypothesis is strongly supported by three facts, namely, the sum of independent self-similar processes, the random splitting of self-similar processes, and the output process of a deterministic service time queue with self-similar input are all self-similar.published_or_final_versio

A unified concurrency control algorithm for distributed database systems

We present a unified concurrency-control algorithm for distributed database systems in which each transaction may choose its own concurrency control protocol. Specifically, they integrate two-phase locking, timestamp ordering, and precedence agreement into one unified concurrency-control scheme. They show the correctness of the scheme and study the problem of selecting the best protocol for each transaction to optimize system performance.published_or_final_versio

Decomposition of network of queues with self-similar traffic

Jackson's network of queues model greatly simplifies the performance analysis of telecommunication networks with Poisson traffic arrivals and exponential service times. It reduces the analysis of a network into the analysis of individual communication links, each of which may be modeled as an M/M/m queue. Motivated by the growing significance of self-similar traffic in modeling broadband network traffic, we propose a new network of queues model for telecommunication networks. Our model resembles Jackson's model except that the arrival is self-similar and the service time is deterministic. It captures the characteristics of modern high speed cell-based networks. We hypothesize a result analogous to Jackson's Theorem, that each mode of this network model behaves as a G/D/1 queue with self-similar arrival. Based on this hypothesis, many network-wide performance measures, such as the end-to-end delay, can be evaluated in a simple fashion. Our hypothesis is strongly supported by three facts, namely, the sum of independent self-similar processes, the random splitting of self-similar processes, and the output process of a deterministic service time queue with self-similar input are all self-similar.published_or_final_versio

QuIVeR: A class of interactive video retrieval protocols

Video-on-demand (VOD) servers need to be efficiently designed in order to support a large number of users viewing the same or different videos at different rates. In this paper, we propose the Quasi-static Interactive Video Retrieval (QuIVeR) Protocol for this purpose when disk-array based video servers are used. Five variations - QuIVeR-1, QuIVeR-2, QuIVeR-3, QuIVeR-4 and QuIVeR-5 - are presented. The properties as well as the relative merits and demerits of each protocol are discussed. The protocols require no buffer at the server and hence, all retrieved segments are immediately transmitted to the appropriate users. The amount of buffer required at each user's set-top box is reduced to two video segments. Guarantees are provided for the avoidance of video starvation as well as buffer overflow at each user's set-top box. Numerical results, obtained using data from an MPEG coded `Star Wars' video, are provided.published_or_final_versio

Renegotiated CBR transmission in interactive video-on-demand system

An Interactive Video-On-Demand (IVOD) system requires transmission bandwidth allocation for each user. Since the volume of data in each video frame is variable, dynamic bandwidth allocation is desirable. In this paper, a new scheme that dynamically determines required bandwidth based on the queue length at the viewers Set-Top Box (STB) is proposed. This method requires no pre-calculation, so it is easily applied to IVOD. The variance of the video transmission rate for each user is an important factor as it affects the service quality of other multiplexed traffic. It is desirable that the transmission rate is changed gradually. A multi-layer concept is introduced to achieve this. Through numerical evaluation using actual movie data, we demonstrate that the variance of the transmission rate is close to the optimal value and the bandwidth utilization is close to unity.published_or_final_versio