Edwin M. Sawan

A new medium access protocol for RFID networks with foresight

In the world where automating jobs is becoming a norm it is no surprise that the interest in RFID networks has grown exponentially. With RFID technology companies around the world can reduce their workforce and grow their business. However, this technology is not at that maturity point yet. In order for a cart full of groceries to go through an unmanned checkout lane, it is crucial that all of the tagged items are read and processed with 100% reliability. Also the process time needs to be short so that customers complete their purchases as fast as possible. In order to achieve time and reliability, several transmission control protocols have been devised. Out of these, the transmission control protocol that is most popular with RFID equipment manufacturers is EPCglobals Class 1 Gen2. The transmission control in EPC C1G2 is achieved by framed slotted ALOHA where tags pick a random slot from the choices given by the reader and when their turn comes, they backscatter their information. This can lead to many empty slots and many collision slots apart from the successful slot. The time spent on these non-successful slots is studied in [4] and in this paper we extended the concept provided in [4] and propose a new method that scans for the empty and collided slots before attempting to read tags.

LQ design for two-time-scale systems by unified approach using delta operators

We present a linear quadratic design for singularly perturbed systems by a unified approach with /spl delta/ operators. We convert a two-time scale discrete system to a two-time-scale unified system and solve the problem and compare the results of the two systems.

Distributed AF beamforming relay networks under transmit power constraint

This paper investigates minimum mean square error (MMSE)-based amplify-and-forward (AF) relay amplifying matrices and source/destination beamforming vectors under perfectly known channel state information by imposing constraints on the transmit power of source and relays, separately and individually. The main contribution of this paper is the derivation of a set of relay amplifying matrices and source/destination beam-forming vectors under transmit power constraints on the source and relay. Additionally, the SNR and the MMSE cost function behaviors will be investigated numerically and analytically.

Mobile Relay Amplifying Matrix Design of the Cooperative Distributed MMSE Relaying for AF Wireless Mobile Networks

This paper presents an optimal amplify-and-forward (AF) relay scheme for a multiple-input-multiple-output (MIMO) system consisting of M-mobile sources, M-mobile destinations, and N-cooperative distributed mobile relay nodes. A wireless mobile relaying network with channel state information is investigated. The received signals from the mobile sources are ex- changed between mobile relays to achieve optimal performance. The main contribution in this paper is the derivation of mobile relaying amplifying matrices (MARMs) designed for cooperative MIMO networks based on the minimum mean square error (MMSE) criterion. By adopting the new proposed MRAMs, the bite error rate (BER) performance of the system is evaluated using Monte-Carlo simulations.

H-infinity design for two-time-scale systems by unified approach using delta operators

We implement the unified approach using delta operators in the standard H-infinity problem for two-time-scale systems in the frequency domain. By a unified approach using a delta operator, the procedure and result for the solution is shown to be simpler and more accurate than those of a discrete system using shift operators.

Two-way MMSE strategies for AF distributed relay networks under power constraint

This paper proposes amplify-and-forward (AF) relay strategies for two-way wireless distributed relay networks consisting of two sources with a single antenna per source and multiple N relays with a single antenna per relay. The objective of this paper is to determine optimal relay amplifying matrices (or vectors) under global and local power constraints at the relays based on the minimum mean square error (MMSE) criterion with/without the perfect cancelation of self-interference. With the derived optimal relay amplifying vectors, performances of the proposed two-way AF distributed relay system are investigated by presenting average bit error rate (BER), average MMSE behavior, and the sum of the achievable rate.

Channel uncertainty for AF wireless distributed relay networks under power constraint

This paper presents optimum relay amplifying matrices (or vectors) using the minimum mean square error (MMSE), maximum signal-to-noise ratio (SNR), zero-forcing (ZF), and matched-filter (MF) criteria for an amplify-and-forward (AF) wireless distributed relay network with a one-source-one-destination pair and iV-relay under the global power constraint (GPC) at the relays in a channel uncertainty (CU) environment. In addition, the local power constraint (LPC) at the relays is also considered for the MMSE criterion. With the derived optimum amplifying relay matrices, cost function and SNR behaviors, achievable rate, and relay selection scheme in the CU environment will be investigated theoretically and evaluated numerically.

Two-Way AF Wireless Relay Networks under Channel Uncertainty

Two different two-way amplify-and-forward (AF) wireless relay systems with transmit power constraints at the relay(s) are studied: one- relay system with multiple N antennas between two sources, and multiple N-relay system with one antenna per relay between two sources. The iterative and explicit relay amplifying matrices (or vectors) with perfect cancelation of self- interference under channel uncertainty are determined based on the minimum mean square error (MMSE) criterion. Both iterative and explicit relay amplifying matrices are numerically investigated through the simulation. Simulation results show that the gain of diversity order with channel uncertainty can occur as N increases, while the loss of diversity order can occur as channel estimation error powers increase.

Distributed multiuser MMSE relaying strategies for AF wireless relay networks

This paper proposes minimum mean square error (MMSE)-based amplify-and-forward (AF) relay amplifying matrices under perfectly and imperfectly known channel state information by imposing a constraint on the transmit power of the relays. The main objective of this paper is to determine optimal relay amplifying matrices with and without channel uncertainty under the transmit power constraint at the relays. Additionally, by using the derived optimal relay amplifying matrices, it is proven that the better BER performance is observed when power is constrained at the relays during data transmission, compared to the no-power constraint case in [6]. Finally, simulation results show that the MMSE cost function values with and without channel uncertainty are always less than the number of sources and destinations (M), regardless of the number of relays (N).

Power Allocation for AF Relaying Network under Channel Phase Misalignment

This paper studies both cooperative and noncooperative amplify-and-forward (AF) wireless relay strategies with power constraints at the source and at the relays. The main objective is to design jointly and iteratively the closed form of a source scaling factor and a relay amplifying matrix, based on the minimum mean square error (MMSE) criterion under the conditions of both no-channel and channel phase misalignments. With the derived optimal source scaling factors and relay amplifying matrices, impacts on the system performance of both no-channel and channel phase misalignment are investigated by presenting the bit error rate and cost function behavior. Finally, this paper presents the iterative algorithm to solve the constrained Lagrangian optimization problem with a low computational complexity.