Yu T. Su

Analysis of packet interference and aggregated throughput in a cluster of Bluetooth piconets under different traffic conditions

In a Bluetooth piconet, the Master essentially controls the channel. Due to an absence of coordination between independent Masters while accessing the wireless medium, devices will encounter high packet interference if several piconets are simultaneously operating in the same area. Since even a headset and a mobile phone can be connected with a Bluetooth link forming a piconet, it may not be unusual to find tens of independent piconets in crowded places like airports, international conferences, shopping malls, and so on. Study of packet interference is important because interference affects the throughput of a piconet. Motivated by the fact that applications will benefit, in terms of higher available data rate in one direction, by using multiple-slot packets in an asymmetric manner, in this paper, we present an analytical model of packet interference in a cluster of piconets using multiple-slot packets. Also, considering that all the portable devices can have a Bluetooth interface and people are highly mobile these days, it will not be uncommon to find a cluster of piconets of both the 79-hop and the 23-hop types in the same area. We then present an analytical model of interference of multiple-slot packets in a heterogeneous cluster of Bluetooth piconets. By a heterogeneous cluster we mean some piconets are of the 23-hop type and the rest are of 79-hop type. We show how the aggregate throughput in a cluster of piconets degrade under various traffic scenarios, such as 1-slot, 3-slot, and 5-slot packets in symmetric and asymmetric modes in synchronous and asynchronous conditions of Master clocks. Our analytic model is based on the idea of probabilistic graphs, where a node denotes a piconet and an edge denotes the probability of interference between two nodes. Though the 23-hop system has been phased out, our work gives a general approach to model packet interference in multiple, frequency-hopping systems that need not be Bluetooth systems.

Packet interference in a heterogeneous cluster of Bluetooth piconets

In a Bluetooth piconet, the master essentially controls the channel. Due to an absence of coordination between independent masters while accessing the wireless medium, devices will encounter high packet interference if several piconets are simultaneously operating in the same area. Since even a headset and a mobile phone can be connected with a Bluetooth link, forming a piconet, it may not be unusual to find tens of independent piconets in crowded places like airports, international conferences, shopping malls, and so on. The study of packet interference gains importance, because it affects throughput of a piconet. Considering that all the portable devices can have a Bluetooth interface and people are highly mobile these days, it is not uncommon to find a cluster of piconets of both the 79-hop and the 23-hop types in the same area. In this paper, we present an analytical model of packet interference in a heterogeneous cluster of Bluetooth masters. By a heterogeneous cluster, we mean a cluster of piconets consisting of 23-hop and 79-hop types. Our analytic model is based on the idea of probabilistic graphs, where a node denotes a piconet and an edge denotes the probability of interference between two nodes.

Adaptive blind equalization using second- and higher order statistics

This paper presents two classes of adaptive blind algorithms based on second- and higher order statistics. The first class contains fast recursive algorithms whose cost functions involve second and third- or fourth-order cumulants. These algorithms are stochastic gradient-based but have structures similar to the fast transversal filters (FTF) algorithms. The second class is composed of two stages: the first stage uses a gradient adaptive lattice (GAL) while the second stage employs a higher order-cumulant (HOC) based least mean squares (LMS) filter. The computational loads for these algorithms are all linearly proportional to the number of taps used. Furthermore, the second class, as various numerical examples indicate, yields very fast convergence rates and low steady state mean square errors (MSE) and intersymbol interference (ISI). MSE convergence analyses for the proposed algorithms are also provided and compared with simulation results. >

Adaptive VSS blind equalizers

It is well known that an adaptive filter with a large step size in the transient period and a small one in the convergence period gives small mean squared steady state error while achieving a fast convergence rate. Based upon this idea, we present two variable step size (VSS) blind equalizers. The first one employs an intersymbol interference (ISI) estimator to control the step size, the second algorithm uses a mean squared error (MSE) estimator to adjust the step size. Both accomplish what has been expected.

Cutoff rates of multichannel MFSK and DPSK signals in mobile satellite communications

This paper studies the coded performance of multichannel MFSK and DPSK signalings in mobile satellite environments characterized by various kinds of multipath fading. Rician, Rician/lognormal, and a convex combination of Rician and Rician/lognormal or Rayleigh/lognormal distributions are used to model these communication channels. We investigate the minimum average signal-energy-to-noise ratio required to yield a cutoff rate that is greater than or equal to a given code rate. Also examined are system design issues such as the effect of quantization and metric conversion, the choice between binary codes and M-ary symbol codes, the optimization of the diversity order and the signal size, and the order of deinterleaving and diversity combining. Numerical examples are given to answer concerns raised by these issues. >

Analysis of packet interference in a cluster of Bbluetooth piconets under different traffic conditions

Study of packet interference is important because interference affects the throughput of a piconet. Motivated by the fact that applications will benefit, in terms of higher available data rate in one direction, by using multiple-slot packets in an asymmetric manner, in this paper, we present an analytical model of packet interference in a cluster of piconets using multiple-slot packets. Also, considering that all the portable devices can have a Bluetooth interface and people are highly mobile these days, it will not be uncommon to find a cluster of piconets of both the 79-hop and the 23-hop types in the same area. We then present an analytical model of interference of multiple-slot packets in a heterogeneous cluster of Bluetooth piconets. By a heterogeneous cluster we mean some piconets are of the 23-hop type and the rest are of 79-hop type. We show how the aggregate throughput in a cluster of piconets degrade under various traffic scenarios, such as 1-slot, 3-slot, and 5-slot packets in symmetric and asymmetric modes in synchronous and asynchronous conditions of master clocks. Our analytic model is based on the idea of probabilistic graphs, where a node denotes a piconet and an edge denotes the probability of interference between two nodes.

Interference rejection and equalization in band-limited channels

1988 was summarized in [21 while recent efforts in In addition to thermal noise and intersymbol interference (ISI), a transmitted wideband signal of a wireless communication system may sufler from interference caused b y other cochannel narrowband users or other radio frequency interference (RFI). Although spread spectrum (SS) signals is inherently resistant to interference the system performance would be greatly enhanced i f we can eliminate most of the interference before despreading or demodulation takes place. This paper provides a workable solution for direct sequence systems when the channel can be modeled as an FIR filter a n d the narrowband interference (NBI) is either multiple CW tones, or an A R process driven b y a white Gaussian sequence. Unlike earlier solutions, the proposed NBI rejection scheme is based on a cost function evaluated at the output of the PN despreader. It is simpler to implement and is capable of removing ISI. When the de lay spread of the multipath channel is comparable to a bit time our proposal renders better BER performance.

A random graph-based model to analyze packet interference between frequency hopping systems with an application to Bluetooth

In this paper, we present a graph-based model for analyzing interference between two frequency hopping systems for wireless communication. Informally, frequency hopping means that successive packets are transmitted on different frequencies from a pseudo-random sequence. The frequency band occupied by a packet may be narrow or wide. Our model is based on the concept of probabilistic graphs, where a node represents a channel and an edge denotes the probability of interference between two packets belonging to two different channels. Two packets on two channels are said to be mutually interfering if the two packets overlap in time and are transmitted on the same frequency. Thus, from the viewpoint of probabilistic graphs, the expected number of nodes with at least one incident edge is a measure of packet interference in a collection of wireless channels. We apply this model of packet interference to a heterogeneous cluster of Bluetooth piconets, where a piconet could be either of 79-hop type or of 23-hop type. Though the 23-hop type has been phased out, we use it as an example in this paper.