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A Study on the Performance Evaluation of Forward Link in CDMA Mobile Communication Systems
Abstract
In the CDMA cellular mobile communication systems, the connection between base and mobile station has a forward link from base station to mobile station. Four channels of forward link, pilot channel, sync channel, paging channel, traffic channel, have an absolute influence on forward coverage and speech quality. And overhead channels(pilot, sync, paging) are assigned output at the adequate rate to optimize the structure of coverage and to minimize the influence of neighbor base station. And the quality of forward link depends on the size of received field strength, as well as Ec/Io which includes both self signal and all noise factors affecting self signal is the main standard in order to decide the coverage and quality of forward link. In this paper, in order to improve a performance of forward link systems in the mobile communications using CDMA, I examine influencing factors in forward links, and measure at LAB., and analyze their results. As the results, I confirm that identify their effect.
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A scheme for channel impulse response estimation is proposed for
next generation direct sequence code-division multiple-access (DS/CDMA)
systems where a pilot channel is simultaneously transmitted with a data
traffic channel in the reverse link. In contrast to a conventional
scheme utilizing only pilot channel for channel estimation, the proposed
scheme exploits channel information in both the pilot and data traffic
channels by combining channel estimates from these two channels. The
combining coefficients are derived to minimize the channel estimate mean
square error. The proposed schemes are found to improve significantly
the channel estimation accuracy and BER performance through analysis and
simulations
We propose an improved sectorization scheme, called narrow-beam
quad-sector cell (NBQC) for cellular networks, in which each cell is
divided into four sectors and each sector is covered by a 60°
antenna. The NBQC structure allows easy implementation of the concept of
interleaved channel assignment (ICA), which can take full advantage of
antenna directivity. With ICA, the NBQC system can enhance the system
performance from several perspectives. First, the NBQC has better
coverage performance than the current three-sector cellular
architecture. Second, we demonstrate that in a typical radio
environment, the NBQC system ran achieve a reuse cluster size N=2 with
the signal-to-interference ratio (SIR) as high as 11 dB in 90% of the
cell area, which is a 3-5-dB improvement over the existing cellular
architectures. Third, as compared to the most advanced three-sector
clover-leaf cell architecture with reuse cluster size N=3, the NBQC
system with ICA can achieve reuse cluster size N=2 with very slight
degradation in SIR performance, thereby still improving the system
capacity by about 10% over a wide range of ninetieth percentile SIR
requirements
We propose a network architecture for code-division
multiple-access (CDMA) cellular systems based on adaptive sector
coverage. We show that there is a capacity limit for a CDMA system,
which for a soft limit is fairly hard. We also show that for
nonhomogeneous traffic, changing the area of coverage for each sector in
a sectored-cell can absorb the dynamics of the traffic. For a cell of a
fixed radius, divided into n sectors, it is possible to select the
angles of coverage of each sector in order to avoid excessive blocking
due to temporary nonuniformity of traffic across the cell. This result
is based on the fact that for a given set of system parameters
(bandwidth, bit rates, Eb/N0 etc.), a certain
amount of area is covered. Hence, the exact shape of the cell/sector is
not important. The idea presented is shown to be applicable to
overlapping sectors
Non-uniform traffic can affect communications quality in microcell systems, and this disparity in communications quality between base stations (BSs) lowers the system efficiency in CDMA systems. If traffic distribution and propagation conditions are already known during the introduction of a CDMA system, it is desirable to design cell areas according to the non-uniformity of traffic distribution and BS locations. Cell area is determined by the transmission power of the pilot-signal from the BS and it is necessary to control the transmission power of mobile stations in the uplink, which is determined by the desired power level at the BS, according to the cell area. The disparity in communications quality can be rectified by optimally designing the two parameters of the pilot-signal power and desired power level. This paper describes an algorithm for setting both the pilot-signal power and the desired power level during the cell design stage in CDMA systems. The proposed algorithm operates that the communications qualities of all BSs in the system converge to average quality by adjusting the two parameters. The parameters of all BSs in the whole system can be determined through computer calculation. Through performance evaluations, we confirmed that the average SIRs of all BSs attained almost the same value and the variance between the BSs was less than half by adopting the cell design algorithm when there was dispersion in BS placement. This algorithm is also effective using the actual measured SIR after a system has been established.
From the Publisher:Understand the essentials of CDMA wireless technology and develop the knowledge you need to design and operate either co-located AMPS and CDMA or dedicated CDMA systems with this unique reference. Drawing upon his recent experience in building the first major CDMA network in North America, the author helps you acquire the knowledge you need to engineer and implement an IS-95 based CDMA system. Examining both the theoretical and practical side of CDMA engineering, this comprehensive guide is an excellent resource for practicing RF and system engineers who will find the modular-oriented chapters on spread-spectrum multiple access technique, design and performance engineering, CDMA traffic engineering, and regulatory implications especially useful. Engineering managers and directors seeking proficiency in CDMA technology will appreciate the author's ability to supply a "big picture" perspective where only the most important and relevant information to designing and optimizing a CDMA system is presented. A systemic approach makes this an ideal book for use in technical training and academic classes.
From the Publisher:Here's the second edition of the classic reference in the field,Mobile Cellular Telecommunications Systems. From highly respected industry pioneer William Lee,this thoroughly updated reference provides a complete technical description of the design,analysis,and maintenance of cellular systems. To reflect the many changes cellular technology has undergone in the past five years,the second edition features new chapters on the CDMA standard,microcell systems,and digital cellular systems,along with updated coverage of the practical concepts,design techniques,and operation of mobile cellular systems for telecommunications engineers and technicians.
CDMA cellular mobile communication service needs to offer good quality of services (QoS) and coverage for new and sophisticated
power control to achieve high capacity. In this paper, in order to efficient cell sector and to improve the Ec/Io of the pilot
channel in CDMA mobile communication systems, we analyze and compare the wide-beam trisector cell(WBTC) with the narrow-beam
trisector cell(NBTC) as a method for cell sectorization. The NBTC method was compared with the WBTC method, using the results
of both a theoretical analysis and a simulation, in order to examine its effectiveness and validity. As a result, we confirm
that efficient cell sector method to minimize interference from adjacent base stations and to increase cell coverage.
The authors study the capacity of a CDMA-based microcellular
wireless system in the base to portable (downlink) direction. Narrowband
CDMA with system bandwidth of 1.25 MHz is considered. Coherent reception
using a pilot signal, BPSK modulation with 1/2 convolution codes, and
power control are considered. Capacity of the downlink is evaluated as a
function of multipath diversity, path loss exponent, and power control
strategies. Both slow and fast power control on the downlink are
considered. With slow power control, the capacity is severely limited.
It is observed that fast power control significantly improves the
capacity of the downlink. Finally, the effect of path loss exponent on
the downlink capacity is illustrated
A scheme for channel impulse response estimation is proposed for
next generation DS/CDMA systems where a pilot channel is simultaneously
transmitted with a traffic channel in the reverse link. Through analysis
and simulation, the proposed scheme is found to significantly improve
channel estimation accuracy and BER performance
This article describes a wideband spread code-division multiple
access (W-CDMA) system for high-capacity and high-quality personal radio
communication. This system has been authorized as an EIA/TIA Interim
Standard IS-665, T1P1 Trial Use Standard J-STD-015, and ITU-R
Recommendation M 1073. The system uses wideband spreading to accomplish
good interference immunity, high-quality speech, and high-speed data
transmission. The system uses coherent detection (CD) and an
interference canceller system (ICS) to enhance the capacity. The CD and
ICS use continuous pilot signals in the forward/reverse links to
estimate the propagation path parameters. PN and Hadamard sequences are
used as the spreading code for minimal mutual interference between
traffic and pilot/sync/paging channels. A robust 32 kb/s waveform speech
coder, ITU-T COM101+, has been developed to achieve toll-quality speech
in the radio environment. This system provides up to 128 voice channels
per cell and data transmission up to 64 kb/s by 5 MHz spreading.
Unification of low- and high-mobility applications and reduced
complexity of system and hardware configurations are accomplished
The ways in which microcell systems can help cellular operators face a number of challenges to achieve continued growth, including the need for increased system capacity, enhanced coverage, lower network cost per subscriber, improved performance, delivery of innovative value-added services, and well-planned equipment and service migration strategies, are discussed. It is argued that microcells must work with conventional cellular systems with lower equipment costs per subscriber, and should require only minimal preinstallation RF design and engineering. Keys to cost-effective microcell deployment are high-performance RF component and digital signal processing technology, efficient radio resource management, optimized distributed network design, and effective switch and network integration.< >
Direct-sequence code division multiple access (DS-CDMA) has become
one of the favourite candidates for future mobile radio communication
systems. The uplink of a coherent DS-CDMA system is investigated. The
channel estimation is carried out via a control channel, which is
transmitted simultaneously to the data channel. This concept is very
closely related to the CODIT-CDMA concept. In the channel estimation, an
averaging process is involved, which for long averaging periods,
suppresses the noise influence efficiently. On the other hand, long
averaging intervals lead to systematic errors in the estimated channel
coefficients due to the time-variant behavior of the channel. Taking
into account these effects, a closed-form analysis of the data-channel
symbol-error rate (SER) is presented. This analysis allows the
prediction of the system's performance and helps to optimize the
parameter settings for channel estimation
Smart Antennas for CDMA Wireless Systems
- T Rappaport
- J Liberti
- T. Rappaport