A dynamic CDMA network for multicore systems

Using spread spectrum signals transmitted from each cell in the CDMA network it is possible to estimate a mobile's location. This location information may be used for directing users to a required destination. Possible uses are emergency calls and fleet management. The performance of a mobile positioning application using the CDMA (code division multiple access) network is investigated through the use of simulation. A CDMA network was first proposed by QUALCOMM and performance tests have been successful. As an additional feature, mobile positioning can be applied to the network at no major hardware cost.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper describes a robust mobile u-healthcare system with multiple physiological signs measurement capability in real time with integration of WSN(wireless sensor network) technology and CDMA(code division multiple access) network. A cellular phone receives health data in WSN and performs local physiological signs analysis at a phone processor, and then transmits abnormal data to server for further detail or precise health signal evaluation by a medical doctor over a CDMA network. Physiological signs of the patients are continuously monitored, processed and analyzed locally at cellular phone process to produce useful medical information for diagnosis and tracking purposes. By local simple analysis in cellular phone processor we can save the data transmission cost in CDMA network. By using the developed integrate ubiquitous healthcare service architecture, patients can realize self-health checking so that the prevention actions can be taken earlier. Appropriate self-monitoring and self-management can cure disease and relieve pain especially for patients who suffer from chronic diseases that need long term observation.

In this paper, quality of service (QoS) guarantees for multimedia traffic are provided by means of cross-layer optimization in code division multiple access (CDMA) networks. We develop optimal connection admission control (CAC) schemes with both physical layer signal-to-interference ratio (SIR) and network layer blocking probability QoS constraints. Packet traffic is modeled as a Markov modulated Poisson process (MMPP). We show that the cross-layer CAC problem in packet CDMA networks has a nearly complete decomposability structure, based on which we propose two CAC algorithms that require much less computation than some existing schemes and can have good approximation to the optimal solutions. The effectiveness of the proposed schemes is demonstrated by numerical examples.

This paper presents and evaluates the performance of a temporal dynamic spectrum allocation (DSA) scheme based on the CDMA networks as an alternative to the fixed spectrum allocation (FSA) methods. The paper considers the spectrum allocation between two code division multiple access (CDMA) systems with different time-varying traffic pattern. The traffic pattern is based on the real CDMA traffic data from Daegu urban area in Korea. A proposed algorithm is investigated by the simulation based on CDMA call processing and shows that can produce significant gains for the radio access network (RAN) in DSA.

An enhanced adaptive scheme based on threshold method with a reduced complexity that combine adaptive modulation and coding with diversity combining is presented for throughput maximization in broadband code division multiple access (CDMA) satellite networks. The proposed algorithm is a modify, enhanced, and more robust version of the existing algorithms for adaptive transmission rate and modulation in CDMA networks. The rate compatible punctured turbo-coded (RCPT), which has been found to give improved throughput performance in a direct sequence (DS) CDMA is exploited. A semi-analytical process and simulations were carried out. It is found that there are significant improvement in the average throughput and the bit-error performance. The proposed algorithm using adaptive coding and modulation (instead of variable spreading gain) outperforms other systems such as Selective Power Control with Active Link Protection (SPC-ALP) algorithm proposed for adaptive transmission rate and power control in CDMA networks.

The position location systems have become a hot issue over the past few years in wireless communication. So far, many people have thought of the Global Positioning System (GPS) as a position location system. But we can use the code division multiple access (CDMA) networks for position location. Two systems considered for position location in CDMA networks are direction finding and ranging. In this paper, we have examined the two systems and analyzed their performance. We also propose a position location system to mitigate the non-line of sight (NLOS) propagation error in IS-95 CDMA networks. We show that the proposed position location system improves the performance for the NLOS ranging error.

The cyclic period and free spectral range of arrayed-waveguide gratings (AWG) in a wavelength-division multiplexing/optical code division multiple access optical code division multiple access network are exploited. The total optical network unit (ONU) of network capacity is partitioned into groups of different wavelength in accordance with the geographical location of subscribers based on the radial distance of the ONU to the optical line terminal. Combining concentric circles round by round for ONU groups enables a fixed round-trip time in the data transmission and a significant increase in system performance. Using AWG router, the proposed topology of concentric circles retains signature orthogonality and minimizes wavelength collisions on the photo-detector. Furthermore, the adoption of extended M-sequence codes corresponding to the AWG codec provides a simpler, more efficient coding procedure and accommodates more users in a single group.

The paper proposes a novel approach for time delay and channel gain estimation for multipath fading Code Division Multiple Access (CDMA) signals using the Unscented Kalman Filter (UKF). Given the nonlinear dependency of the channel parameters on the received signals in multiuser/multipath scenarios, we show that the UKF achieves better performance than its linear counterparts. The UKF, which is a derivative-free Kalman filtering approach, avoids the errors associated with linearization in the conventional Extended Kalman Filter (EKF). The Numerical results also show that the proposed UKF is simpler to implement, and more resilient to near-far interference in CDMA networks.

Multiple access interference (MAI) appears in Code Division Multiple Access (CDMA) systems when the communication channel is a multi-path channel and the spreading codes are not orthogonal. Orthogonality between spreading codes cannot be maintained at the CDMA receiver because the codes may be asynchronous due to channel delay and multi-path spread. The receiver cannot perfectly separate the different signals of the multiple access users, and the resultant MAI limits the capacity of CDMA systems. MAI is a function of the cross correlation property between used spreading codes. In this paper we focus on the cross correlation of the spreading codes, we propose a method to find spreading codes with minimum magnitude of cross correlation. Employing these codes will reduce the resultant MAI in the CDMA system; hence it will increase the system capacity. A great enhancement is shown by comparing found minimum cross correlation spreading codes (MCCSC) with Hadamard and Gold codes.

The introduction of cellphones with poor receiver sensitivity, known as dirty devices, to the Code Division Multiple Access (CDMA) cellular network results in a reduction in cell edge coverage, degraded capacity, and higher drop-call rates. This poor network performance has a negative impact on customer experience and satisfaction, which may result in increased churn for CDMA wireless carriers. Previous research on the impact of dirty devices has used computer-based simulations. This paper demonstrates the influence of dirty devices on a live commercial CDMA network using two distinct approaches. The first approach deploys dirty and non-dirty devices in a live commercial cell, and measures the impact on forward base transceiver station (BTS) power and forward link Ec/Io (Ec is the received pilot chip energy and Io is the spectral density of the total power seen by the device). A series of tests on a live CDMA network with known dirty devices shows an increase in BTS transmit power resources compared with non-dirty devices, leading to the degradation of forward link Ec/Io. The second approach uses a statistical study of the aggregated pilot strength measurement messages reported by the mobile to ascertain the impact of known dirty devices on the overall network Ec/Io of non-dirty devices.

We investigate linear and nonlinear space-time minimum mean-square-error (MMSE) multiuser detectors for high data rate wireless code-division multiple-access (CDMA) networks. The centralized reverse-link detectors comprise a space-time feedforward filter and a multiuser feedback filter which processes the previously detected symbols of all in-sector users. The feedforward filter processes chip-rate samples from a bank of chip-matched filters which operate on the baseband outputs from an array of antennas. We present an adaptive multiuser recursive least squares (RLS) algorithm which determines the MMSE adjusted filter coefficients with less complexity than individual adaptation for each user. We calculate the outage probabilities and isolate the effects of antenna, diversity, and interference suppression gains for linear and nonlinear filtering and for CDMA systems with varying levels of system control (e.g., timing control, code assignment, cell layout). For eight users transmitting uncoded 2-Mb/s quadrature phase-shift keying with a spreading gain of eight chips per symbol over a fading channel with a multipath delay spread of 1.25 /spl mu/s, the performance of a three-antenna feedforward/feedback detector was within 1 dB (in signal-to-noise ratio per antenna) of ideal detection in the absence of interference. By training for 10% of a 5-ms frame, RLS adaptation enabled the same detector to suffer less than a 0.5-dB penalty due to the combined effects of imperfect coefficients and error propagation. The advantage of nonlinear feedforward/feedback detection over linear feedforward detection was shown to be significantly larger for a CDMA system with enhanced system control.

Code Division Multiple Access (CDMA) and multiple input multiple output- (MIMO-) CDMA systems suffer from multiple access interference (MAI) which limits the spectral efficiency of these systems. By making these systems more power efficient, we can increase the overall spectral efficiency. This can be achieved through the use of improved modulation and coding techniques. Conventional MIMO-CDMA systems use fixed spreading code assignments. By strategically selecting the spreading codes as a function of the data to be transmitted, we can achieve coding gain and introduce additional degrees of freedom in the decision variables at the output of the matched filters. In this paper, we examine the bit error rate performance of parity bit-selected spreading and permutation spreading under different wireless channel conditions. A suboptimal detection technique based on maximum likelihood detection is proposed for these systems operating in frequency selective channels. Simulation results demonstrate that these code assignment techniques provide an improvement in performance in terms of bit error rate (BER) while providing increased spectral efficiency compared to the conventional system. Moreover, the proposed strategies are more robust to channel estimation errors as well as spatial correlation.

Mobile robotic technology and its application in various field is currently an area of high interest. Especially, the progression of a mobile robot and communication techniques enables intelligent robots to be developed with more versatile applications. Telerobotic techniques combine robotic systems with remote control technology to enable the performance of task which is impossible or hazardous for human to perform directly. Through these ubiquitous robot controls, the paradigm of robot which performs specific tasks remotely has changed into intelligent robots to perform public and individual tasks. The purpose of the SG-Robot(Security Guard Robot) project is in-line with on-going activities towards the development of autonomous robots for security guard design at home. In security industry, ubiquitous robots have provided a variety of information to the user and achieve its duty through the Web. The mentioned project aims at the development of interactive security guard robots, which are able to be operated with a mobile phone. Last year, the interface for telepresence robot has developed over the Web or RF between robots, but these systems have the demerits of limited distance or geographical limit to be established to an internet link. In this paper, we propose the SG-Robot that can be operated and conduct surveillance of the environment around itself anytime/anywhere using wireless communication networks such as CDMA (Code Division Multiple Access) Networks. This robot has the functionalities of detecting and avoiding obstacles, recognizing face, navigating using a map, capturing and compressing image at high speed, transferring image at real time to CDMA phone, and operating remotely by a mobile phone. The goal of these functionalities is to tele-operate robot using a mobile phone anytime/anywhere and to construct the systems that has the home network function, ubiquitous computing, and home security.

An experimental demonstration of a direct-sequence spread spectrum optical code division multiple access (CDMA) network employing differential phase-shift keying modulation is reported. Two approaches to implementing coherent optical CDMA networks are demonstrated with a small test-bed and the results obtained are presented.

Optical code division multiple access (CDMA) maps low information rate electrical or optical signals into high-rate optical sequences to achieve random, asynchronous multi-access. In optical CDMA, many nodes transmit simultaneously in the same frequency band. Accordingly, signals must be designed to reduce interference. In order to reduce interference among signals to acceptable levels, their bandwidth would be several orders of magnitude greater than the information bandwidth 1/T of the digital modulation; T being a bit duration. In order to do this, each bit is sub-divided into a number of binary chips. The chip sequence constitutes a code that permits a bit stream broadcast on a network to be selected by means of a correlation process at the receiver destination. A large number of chip codes can be assigned to different users. The set of optical sequences essentially becomes a set of address codes or signature sequences for the network. The advantage of CDMA is that it is a true tell-and-go protocol. When one node wants to send traffic to another node, prior coordination is required only with that node. Multiple users can simultaneously access the channel with no waiting time, in contrast to other asynchronous protocols like CSMA or CSMA/CD where each user must wait for the channel to become idle before gaining access. A CDMA network is also highly scalable and modular.