Forward link handoff distribution with correlated lognormal fading

We present linear precoding methods for downlink transmission in multi-user multiple-input multiple-output (MIMO) systems where channel state information (CSI) can be obtained through training. In this paper, channel training overhead and estimation error are rigorously accounted for while determining the net system throughput. First, we consider the case with training on the reverse link only. We study a precoding method which is a combination of two schemes: selection of users with largest estimated gains and zero-forcing to selected users. Next, we consider the case with training on both reverse and forward links. We obtain a lower bound on the weighted-sum capacity, and propose an algorithm to determine an efficient precoding matrix. This precoding method effectively utilizes the training on the reverse and forward links in improving net throughput.

We considered call admission control (CAC) algorithms both for the reverse and forward link with multiple types of services requiring different SIRs (signal to interference ratio) and transmission rates. In the forward link, a call is admitted if the requested power is available at the base station, whereas in reverse link, a call is admitted if the interference level is below a certain revel that guarantees the communication quality. First, the optimal power ratio that characterizes the effect of different service types is considered. Then a simple CAC algorithm is proposed and evaluated through simulation. With these CAC algorithm, we compare the capacity of forward link and reverse link for commonly used SIR equations.

The authors present a novel cell structure that combines the qualities of code division multiple access (CDMA) and time division multiple access (TDMA) to reduce cochannel interferences. The cell consists of a centrally located base station with eight surrounding corner antennas. The mobiles and antennas operate in a TDMA mode and the communication channels employ spread spectrum direct sequence modulation. TDMA combined with the spatial separation of the cell antennas reduces the carrier-to-interference ratio and thereby increases the cell capacity. The capability and cochannel interference for both forward and reverse link of the proposed system are computed and compared with that of the traditional CDMA cellular system. The results show that the capacity of the proposed system in the forward link is increased by an average factor of three over the traditional CDMA cellular system. For the reverse link the capacities of the systems are comparable. >

Third generation (3G) wireless networks have been designed to provide high speed data services on both forward and reverse links. In addition to increased data capacity they also support QoS (quality of service) guarantees for user applications. Users may run multiple applications (service instances) simultaneously and QoS guarantees must be assured for one or more of them. In order to maintain these QoS guarantees for each user's service instance, the radio resources assigned to the mobile must be adjusted in real time. However, the forward packet data channel in 3G systems are time-shared among all mobiles. Furthermore, the forward link channel conditions of the mobile changes over time. This implies that the forward link throughput available to the mobile is stochastic. In this paper, we address the linkage between the application demands (i.e., based on the QoS attribute guarantees) and the available channel capacity (i.e., resources assigned by the scheduler) and present a simple solution to the problem.

We study the performance of a fixed‐beam system in the forward link of IS‐95 CDMA systems by means of Monte Carlo simulations. The simulations are performed using a comprehensive model of the forward link which includes correlated shadowing, soft and softer handoff, and transmit power allocation. The effects of user distribution, soft/softer handoff threshold, and multipath diversity are examined. We find that the availability of signal diversity plays an important role in the system performance. When the soft handoff threshold is decreased from ‐12 dB to ‐18 dB, capacity increases by 15%, but handoff overhead more than doubles. When fifty percent of users have 2‐ray multipath, capacity increases by 18%. Thus, the availability of multipath in the system has a dramatic influence on forward link capacity. A non‐uniform distribution using a “highways” model reduces capacity by more than a half. This shows that for successful implementation of a fixed‐beam system, it is important to plan cell sites in a way that keeps loading uniformly distributed in azimuth.

Many analytical approaches have been proposed for handoff analysis because handoff is an important technology in mobile communication systems. In CDMA systems with soft handoff, mobile stations (MS's) within a soft handoff region (SR) use multiple radio channels and receive their signals from multiple base stations (BS's) simultaneously. Therefore, SR size, MS's speed and arrival rate of calls have very great influence on handoff process. In this paper, we study the performance of soft handoff in CDMA systems where is based on the square model. The effects of SR size, MS's speed and call arrival rate on call blocking probability are investigated. The results are compared with hard handoff.

A detailed and realistic time-varying channel model is used in the simulation of a 20-Mbps indoor wireless communication system that uses a DFE on the reverse link and a Tomlinson-Harashima (1971, 1972) precoder on the forward link to mitigate ISI. The motivation of such an asymmetric scheme is to minimize the hardware complexity of the portable unit. Results confirm the viability of this system by quantifying the performance of the forward link as a function of time, portable speed, channel delay spread, transmission distance and training duration. Additionally, a simple and effective scheme for receiver AGC at the portable is proposed and evaluated.

On performance of multi-RIS assisted multi-user nonorthogonal multiple access system over Nakagami-[formula omitted] fading channels

This paper proposes broadband packet wireless access focusing on the data link layer incorporating the IP-based core network, employing variable spreading factor-orthogonal frequency and code division multiplexing (VSF-OFCDM) with two-dimensional spreading that prioritizes time domain spreading in the forward link and multi-carrier/DS-CDMA (MC/DS-CDMA) in the reverse link for the system beyond IMT-2000. Based on the aforementioned wireless access schemes, we present inter-cell and inter-sector slow cell selection tracking shadowing variation, which is advantageous to the router-based IP core network due to its slow hard handover feature. We propose several data link control methods: adaptive radio link parameter control in the physical layer according to the quality of service (QoS) requirement, random access channel based short and long packet transmission (note that message part of random access channel is used for reservation) in the reverse link, and a maximum carrier-to-interference power ratio (CIR) based fast packet scheduling algorithm with assuring minimum throughput for access users while still maintaining fairness of packet assignment in the forward link. Furthermore, we present the throughput performance in the forward link employing Type-II hybrid ARQ called incremental redundancy coupled with the adaptive modulation and channel coding scheme with turbo coding to show a peak throughput above 100 Mbps.

Non-Orthogonal multiple access (NOMA) scheme serves as a favorable technology for 5G and beyond cellular networks as compared to orthogonal multiple access (OMA) scheme. Multipath fading also affects the performance of wireless communication system. So as to exploit the features of NOMA technique, it is vital to identify and analyze its performance over various fading channels. This paper provides the performance analysis of NOMA based cellular system over two key parameters named as channel capacity and outage probability. Rician fading distribution has been considered for multipath fading. Rician fading channel is much suitable when at least one communication link fallow a line-of-sight (LoS) path and the signal strength is much stronger than other paths. An analytical expression for channel capacity and outage probability has been derived for considered system model. Mante Carlo simulation has been performed to obtain the simulation results for channel capacity and outage probability using the Rician fading channel. Comparison of simulation results for near and far users have been provided for channel capacity and outage probability.

The traffic performance of integrated 3G wide-band code division multiple access (WCDMA) and GSM/GPRS network is evaluated. This type of network links two cellular radio systems which have different set of frequency bands and the same coverage size. The base station of 3G WCDMA is installed on an existing GSM/GPRS site. Dual-mode mobile terminals use handoff to establish calls on the better system. The soft handoff or inter-frequency hard handoff occurs when mobile terminals of 3G WCDMA or GSM/GPRS move between two adjacent cells, respectively. The inter-system hard handoffs are used between 3G WCDMA and GSM/GPRS systems. The data rate conversions between different systems, soft handoff region size, multiple data rate multimedia services, and the effect of the mobile terminal mobility on the user mean dwell time in each system are considered in the study. The simulation results demonstrate that a great traffic performance improvement on the complementary use of 3G WCDMA and GSM/GPRS cellular radio networks compared with the use of GSM/GPRS cellular radio networks. When high-data rate transmission is chosen for low-mobility subscribers, both the handoff failure probability, and carried traffic rates increase with the new call generation rate. However, both rates decrease conversely with the increasing new call generation rate as soon as the new call generation rate exceeds a critical value. This causes the integrated networks saturation. The higher mean speed for the mobile terminals produces lower new call blocking probabilities and total carried traffic. The new call blocking probabilities and total carried traffic increase with the size of the soft handoff region.

It is shown that the capacities of both the reverse link and the forward link of a code division multiple access (CDMA) cellular system are increased significantly by using a steerable directional antenna on a mobile station. The additional cost for a directional antenna must be taken into consideration for implementation. It is shown that the interference from signals originating beyond the first two cell rings is not negligible for both the reverse link and the forward link. >

SUMMARYThe open radio frequency identification (RFID) air interface may suffer from severe threats that make security problem become a critical issue for RFID systems and applications. This paper proposes a dual cryptography authentication protocol (DCAP) for RFID systems. DCAP partitions randomly the tag identifier into two partial identifiers that are used in the forward link and in the backward link, respectively. The protocol applies hash function and shared‐key encryption algorithm to safeguard both forward and backward links and provides a three‐round authentication mode on each tag and reader in a session. Then, authentication is carried out by the primary, secondary, and final verifications. For a formal analysis, a graphical method Colored Petri Nets is applied to model and analyze the correctness of DCAP. We prove that the protocol owns tag anonymity and forward security and has the capability to resist major attacks such as replay, reader forgery, and tag forgery. Finally, the performance in terms of storage, communication overhead, and computation load is evaluated to demonstrate that the protocol has modest complexity and high efficiency. Copyright © 2011 John Wiley & Sons, Ltd.

In this paper, an exact expression has been derived for the outage probability and the total system goodput of multi-user detection (MUD) based on successive interference cancellation (SIC) for multi-user communication system. We consider a single antenna wireless system with n mobile users and a base station. We focus on the uplink direction with perfect channel knowledge (CSIR) at the base station. We consider slow fading channels where packet outage is the primary concern even if capacity achieving coding is applied. To capture the effect of packet outage, we consider the packet outage probability and the total system goodput of the n users. The analytical expressions for packet outage probability and system goodput are very important for cross layer optimizations of multi-user systems with MUD. However, due to the SIC processing in the MUD, the outage probability analysis is not trivial as the outage probability of the n users are coupled together. In this paper, we shall propose an analytical approach to evaluate the exact expressions of the packet outage probabilities and the system goodputs for the n users based on ordered statistics. We consider adaptive SIC where an optimal decoding order for the MUD is found per fading slot. Simulation results and discussions are given to verify the analytical expressions. From the results, the system goodput increases with the average user SNR and the number of the users with diminishing returns at large SNR and number of users.

This paper compares the link capacity between GSM and CDMA. Viterbi's paper (see IEEE Journal on Selected Areas in Communications, October 1994) analyzed the CDMA link capacity and found that it can be extended due to the soft handoff operation. When calculating the link budget of CDMA, there is about a 4 dB advantage realistically by utilizing a selective diversity between two neighboring cells in the soft handoff region. A new idea has come from GSM operators that uses a ping-pong handoff arrangement in one handoff region which can achieve the same selective diversity between two neighboring cells. This paper analyzes the performance of this arrangement.