On the Impact of Ultra-Wideband (UWB) on Macrocell Downlink of UMTS and CDMA-450 Systems

Results of the analytical analysis to assess the effect of the ultra-wideband (UWB) emissions on the [universal mobile telecommunication system (UMTS) and code division multiple access systems (CDMA-450)] are presented. The (UMTS and CDMA- 450 systems) normalized range and normalized capacity degradation are evaluated. A free-space propagation model is used to calculate the UWB signal power that interferes with both mobile systems. It is shown that, for the case of a single UWB transmitter, the UMTS can easily tolerate UWB interference when the UWB equivalent isotropically radiated power (EIRP) is -92.5 dBm/MHz or less for a distance between the UWB transmitter and the UMTS mobile of 1 m or higher. Also, it is shown that, for the case of multi-UWB transmitters, the UMTS can easily tolerate the UWB interference when the UWB EIRP is -94.5 dBm/MHz. For the single UWB transmitter case, the CDMA-450 downlink can tolerate UWB interference when the UWB power density is in the order of -106 dBm/MHz. For the case of multi-UWB transmitters, the power density that can be tolerated by the downlink of the CDMA- 450 system is in the order of -108 dBm/MHz.     

Multiple access interference and multipath interference analysis of orthogonal complementary code‐based ultra‐wideband systems over multipath channels

In order to alleviate multiple access interference and multipath interference of ultra‐wideband (UWB) system, we propose the orthogonal complementary code (OCC)‐based direct‐sequence UWB system and offset‐stacking (OS)‐UWB system. OCC has perfect partial autocorrelation and cross‐correlation characteristics. With the application of OCC in UWB system, we can obtain better performance in multiple access interference and multipath interference. The proposed OS‐UWB structure can also achieve variable data rate transmission because of its innovative OS spreading technique. Theoretical analysis and simulation results show that the proposed UWB system can achieve excellent performance and outperform the unitary code‐based direct‐sequence UWB system. Copyright © 2013 John Wiley & Sons, Ltd.     

An overview of CDMA evolution toward wideband CDMA

Third-generation mobile radio networks, often dubbed as 3G, have been under intense research and discussion recently and will emerge around the year 2000. In the International Telecommunications Union (ITU), third generation networks are called International Mobile Telecommunications-2000 (IMT-2000), and in Europe, Universal Mobile Telecommunications System (UMTS). IMT-2000 will provide a multitude of services, especially multimedia and high-bit-rate packet data. Wideband code division multiple access (CDMA) has emerged as the mainstream air interface solution for the third-generation networks. In Europe, Japan, Korea, and the United States, wideband CDMA systems are currently being standarized. This article provides a comprehensive introduction to wideband CDMA. It also provides a review of the wideband CDMA air interface proposals including WCDMA in Europe and Japan, cdma2000 in the United States, and wideband CDMA in Korea.     

超宽带多址通信信号的功率谱分析

超宽带(UWB)多址通信是继CDMA技术之后迅速发展的一种宽带传输技术.本文在介绍了各种UWB通信调制方式后,针对产生的UWB多址信号,分析了信号特征,结合数学模型,以简明方式分析了TM-UWB与DSC-UWB多址通信信号的功率谱密度分布,它是UWB通信系统设计与用户干扰分析的基础.     

An Analysis of Interference Mitigation Capability of Low Duty-Cycle UWB Communications in the Presence of Wideband OFDM System

Low duty-cycle (LDC) algorithm is interference mitigation technique, which can reduce the average interference to the existing radio systems by lowering pulse repetition interval or pulse occupation time. In this paper, the coexistence environment between low data rate ultra wideband (UWB) communication system such as wireless sensor network and the existing wideband system using orthogonal frequency division multiplexing (OFDM) such as 4th generation mobile cellular system (4G), worldwide interoperability for microwave access (WiMAX), and field pickup unit (FPU) is considered. In order to analyze the interference mitigation capability of LDC algorithm with impulse based UWB (LDC-UWB) system, the frame error rate (FER) of wideband OFDM system is examined for two types of LDC-UWB system: the signal with random polarity such as binary pole signals and without random polarity such as mono pole signals. We present that LDC algorithm is an efficient interference mitigation technique for low data rate UWB communication via computer simulations regardless of definitions of transmitted energy of UWB communication system, and also that the signal with random polarity is suitable for LDC-UWB system to mitigate interference to the other radio systems. We further investigate the adequate duty-cycle of LDC-UWB system for each definition of transmitted power of UWB communication.     

Base-station antenna array receiver with interference cancellationfor wideband CDMA

The authors present a combining technique of adaptive array antenna and multiple access interference (MAI) cancellation for increasing system capacity in wideband code division multiple access (W-CDMA) systems. From the simulation results, an improvement in system performance proportional to the number of antennas is observed and additional improvement is obtained due to the interference cancellation     

Performance of UWB SSMA using orthogonal PPM-TH over dense multipath channels

In this work we study ultra wideband (UWB) communications over dense multipath channels using orthogonal pulse position modulation (PPM) for data modulation and time-hopping (TH) for code modulation. We consider the effects of the multiple access interference (MUI) in asynchronous spread spectrum multiple access (SSMA) based on random TH codes. We use a realistic multipath channel to analyze the effects of the transmission rate in the number of users for different bit error rate (BER) values.     

Adaptive antennas for MIMO OFDM‐CDMA communication systems

In this paper, we propose symbol‐based receivers for orthogonal frequency division multiplexing (OFDM) code‐division multiple‐access (CDMA) multiple‐input‐multiple‐output (MIMO) communications in multipath fading channels. For multiuser and multipath fading environments, both intersymbol interference and multiple‐access interference must be considered. We propose narrowband and wideband antennas and Wiener code filter for MIMO OFDM‐CDMA systems. The proposed receivers are updated symbol‐by‐symbol to achieve low computational complexity. Simulation results show that the proposed Wiener code filter can improve the system performance for the proposed adaptive antennas. The wideband antenna can achieve better error‐rate performance than that of the narrowband antenna when multipath effect exists. The convergence rate of the recursive least squares antennas is faster than that of the least mean square antennas. Copyright © 2013 John Wiley & Sons, Ltd.     

Wideband DS-CDMA for next-generation mobile communications systems

Wideband wireless access based on direct sequence code division multiple access aimed at third-generation mobile communications systems is reviewed. W-CDMA is designed to flexibly offer wideband services which cannot be provided by present cellular systems, with various data rates as high as 2 Mb/s. The important concept of W-CDMA is the introduction of intercell asynchronous operation and the pilot channel associated with individual data channels. Intercell asynchronous operation facilitates continuous system deployment from outdoors to indoors. Other technical features of W-CDMA include fast cell search under intercell asynchronous operation, fast transmit power control, coherent spreading code tracking, a coherent RAKE receiver, orthogonal multispreading factor forward link, and variable-rate transmission with blind rate detection. The introduction of the data-channel-associated pilot channel allows W-CDMA to support interference cancellation and adaptive antenna array techniques that can significantly increase the link capacity and coverage. This article presents the radio link performance evaluated by computer simulation. Field experiment radio link performance results are also presented     

Multiuser detection for DS-CDMA UWB in the home environment

We demonstrate the effectiveness of multiuser detection for an ultra-wideband (UWB) pulse based direct sequence spread spectrum system using code division multiple access. Extensive simulations were run using channel soundings of the 2-8 GHz band collected in a residential setting and characterized by a high level of multipath fragmentation. We show that the adaptive minimum mean square error (MMSE) multiuser detection (MUD) receivers are able to gather multipath energy and reject intersymbol and interchip interference for these channels to a much greater extent than RAKE receivers with 4 and 8 arms. We also demonstrate the adaptive MMSE is able to reject a narrowband IEEE 802.11a OFDM interferer, even for signal-to-interference ratio as severe as -30 dB. We show the adaptive MMSE exhibits only a 6 dB penalty relative to the single user case for the heavy multi-access interference (number of asynchronous users equal to spreading code length). The practical RAKE receivers were incapable of effectively rejecting either the strong narrowband interference or the heavily loaded wideband interference. Even more moderate levels of interference caused significant degradation in the performance of the practical RAKE receivers.     

A Satellite Radio Interface for IMT‐2000

This paper presents a new satellite radio interface, satellite code division multiple access (SAT‐CDMA), for the satellite component of IMT‐2000. The SAT‐CDMA was proposed by Korea and was based on wideband CDMA (WCDMA) for a high degree of commonality with the terrestrial component of IMT‐2000. Because a satellite link has a longer round trip delay and a higher Doppler shift than a terrestrial link, we developed new technologies that would make the satellite component especially efficient. We present the main features of the SAT‐CDMA radio interface by focusing on satellite‐specific schemes. We also demonstrate with extensive comparison results the performance of the main technologies in the SAT‐CDMA radio interface.     

基于扩频与跳频的多带OFDM-UWB多址技术

根据多带OFDM-UWB通信系统的特点,提出一种基于扩频与跳频的多址技术。该多址技术将多载波码分多址和跳频多址相结合,构成一种新颖的多址技术-正交频分多址(OFDMA),实现多载波码分多址技术和跳频多址技术的优势互补,此接收机的复杂性明显小于常规时频码的多用户接收机。仿真结果表明,基于OFDMA多址技术方案的UWB系统在系统误比特率性能上优于常规时频码方案约5dB。     

Capacity of the WCDMA System Using High Altitude Platform Stations

In this paper, we provide a method to estimate the capacity of the wideband code division multiple access (WCDMA) scheme using High Altitude Platform Stations (HAPS), and demonstrate the results. This is to validate that the HAPS system is one of the most effective solutions to provide high quality wireless communication services, such as IMT-2000 services. We use a practical system model which describes the HAPS system most appropriately, and this leads to realistic estimation results. We estimate the reverse and forward link capacity of the HAPS WCDMA system and compare it to that of the terrestrial system. The estimation results show that the capacity of the HAPS WCDMA system is about 1.2–1.67 times larger than that of the terrestrial system.     

A Low Noise Figure 1.2-V CMOS GPS Receiver Integrated as a Part of a Multimode Receiver

This paper presents what kind of challenges are posed when a global positioning system (GPS) receiver is being added to a multiradio terminal. The GPS receiver chain is integrated as a part of a multiband and multimode receiver, designed for global system for mobile communications (GSM) and wideband code division multiple access (WCDMA). The hostile radio environment challenges in a terminal level are discussed. Especially, the modifications of the additional GPS mode to an existing receiver ASIC with minor and most necessary changes to the implementation is discussed and presented. The IC is implemented in a 0.13-mum CMOS technology without any analog options. At 1.2-V supply voltage and total power dissipation of 49 mW for the analog signal path, the proposed GPS receiver features a noise figure of 2.2 dB and an out-of-band IIP3 of +24 dBm for the worst-case test scenario, which makes it suitable to cellular handset usage in a demanding interference environment.     

Direct conversion radio for digital mobile phones-design issues, status, and trends

Applications of direct frequency-conversion techniques have been rapidly getting attention of radio designers worldwide. This paper focuses on bringing out key implementation challenges of direct conversion receivers and transmitters targeted for different second- and third-generation mobile phone standards like global system for mobile communication, code division multiple access (cdmaOne and CDMA 2000), and wide-band code division multiple access. Techniques and tradeoffs to arrive at optimal implementation are highlighted. Some of the commercially available application-specific integrated circuits that are based on direct conversion architecture and their salient features are summarized.     

Performance of MIMO-WCDMA Multicellular Networks with Ideal Power Control

The goal of the study presented in this paper is to investigate the performance of a multiple input multiple output network using the wideband code division multiple access physical layer protocol. In this context, several transmission techniques are evaluated by executing independent Monte Carlo simulations in parallel with the help of a developed hybrid system—link level simulator. Moreover, the performance of a proposed technique that is based on the maximization of the desired signal of a Mobile Station (MS) to the total amount of interference caused to the rest of the network is evaluated as well. As results indicate, this technique can achieve up to 45 % transmission power gain for high data rate services compared to the case where only the maximization of the desired MS’s signal is considered.     

Overlay of cellular CDMA on AMPS forward and reverse link analysis

The forward and reverse link capacities of code division multiple access (CDMA) and analog cellular system in North America (AMPS) are derived when they are overlaid. Formulas that describe the relationship between the number of CDMA and AMPS users for a given carrier to interference ratio (C/I) of each are presented. A nonlinear system that reduces the power of narrow-band interference is introduced. Simulation results are presented for one narrow-band interferer     

TH-CDMA-PPM with Noncoherent Detection for Low Rate WPAN

Ultra wideband (UWB) impulse radio (IR) is a prospective transmission technology for low-rate indoor communications, as described in the physical-layer proposals for IEEE 802.15.4a wireless personal area networks (WPAN). Time hopping (TH) code division multiple access (CDMA) is considered as an access scheme' for multiuser UWB-IR systems. The TH- CDMA system widely addressed in the literature adopts binary phase-shift keying (BPSK) with coherent detection, which requires accurate channel estimation and thus increasing the implementation complexity. In this correspondence, we suggest using TH-CDMA-PPM (pulse position modulation) with non-coherent detection to simplify the receiver structure. The influence of different combinations of TH and CDMA processing gains on error performance of the new scheme is analyzed and numerical results are presented for illustration.     

Automated optimization of key WCDMA parameters

This paper validates the feasibility of automated optimization of key wideband code division multiple access (WCDMA) radio resource management parameters using control methods. The parameters are regularly adjusted in order to improve performance. The parameters examined in this study include the total cell transmission power target, the received total interference target, the downlink radio link power maximums, the handover windows and the pilot channel powers. The control was based on expert‐defined rules, which applied specific trade‐off policies and statistics of poor quality calls, blocking, packet queuing, power and interference levels and terminal measurements to qualify the parameter values. The approach was validated using a dynamic WCDMA system simulator with a deployment of macro and micro cells on a city region. Results on automated optimization of single parameters on cell level and results on simultaneous multi‐parameter optimization on cell‐cluster level are presented in this paper. The use of the automated parameter optimization methods was shown to result in a significant increase of capacity in comparison to the default parameter settings. Copyright © 2004 John Wiley & Sons, Ltd.     

空时发射分集CDMA的多径分集接收

本文研究了采用STTD(space time transmit diversity)技术的随机序列扩频CDMA(code division multiple access),在频率选择性慢衰落信道中的单用户RAKE接收机在径数很大情况下的性能,并与没有采用STTD的CDMA系统的RAKE接收机的性能进行了比较.结果表明,STTD技术的采用,增强了多址干扰环境中RAKE接收机的抗衰落性能.本文也给出了由STTD所引入的码间干扰及多址干扰对RAKE接收机性能的影响.