Peter Schramm

Structure and performance of the HIPERLAN/2 physical layer

At present, standards for broadband wireless multimedia communications in the 5 GHz band are being developed in Europe as well as in the USA and Japan. HIPERLAN/2 is an upcoming standard which is being specified by the ETSI Project BRAN and is intended to be finished in April 2000. The physical layers of the three systems will be well-harmonized whereas the upper layer protocols are different. In this paper, the concepts and parameters of the physical layer of HIPERLAN/2 are described. According to the harmonization with the American and the Japanese system similarities and differences are pointed out. Furthermore, exemplary performance results are included and discussed.

Radio interface performance of EDGE, a proposal for enhanced data rates in existing digital cellular systems

The use of alternative modulation to provide Enhanced Data rates for Global Evolution (EDGE) is currently being standardized for GSM by the European Telecommunications Standards Institute (ETSI), and is also adopted for IS-136 evolution by the Universal Wireless Communications Consortium (UWCC) in the USA. In this paper, the currently proposed radio interface for this concept and first link simulation results are presented. It is demonstrated that high-level modulation is feasible with an acceptable increase of complexity, and provides good performance, even if impacts like power amplifier nonlinearity, phase noise, frequency offset etc. are taken into account,.

HiperLAN2: broadband wireless communications at 5 GHz

Solutions for high data rates and local coverage have been developed over a couple of years in the area of wireless local area networking. The quality of service, security, mobility, and high throughput are key components that drive the standards for broadband wireless multimedia communications presently being developed in Europe as well as in the United States and Japan for the 5 GHz band. These technologies are well suited to complement third-generation cellular networks. HiperLAN type 2 (HiperLAN2) is one of these systems, which is being specified by the ETSI project BRAN. The core parts of the specification were finalized at the end of 1999. Almost total harmonization has been achieved between the standardization bodies in Europe and Japan (ETSI and ARIB, respectively). HiperLAN2 will provide data rates up to 54 Mb/s, and is intended for local communications in indoor and outdoor environments. An overview of the HiperLAN2 standard is presented together with exemplary link and system performance results.

Overview and performance of HIPERLAN type 2-a standard for broadband wireless communications

At present, standards for broadband wireless multimedia communications in the 5 GHz band are being developed in Europe as well as in the US and Japan. HIPERLAN type 2 (H/2) is being specified by the ETSI BRAN (Broadband Radio Access Networks) project; the core parts of the specification were finalised at the end of 1999. Almost total harmonisation has been achieved between the standardization bodies in Europe and Japan, ETSI and ARIB, respectively. An overview of the H/2 standard is presented together with exemplary link and system performance results.

Modulation for HIPERLAN type 2

Currently, standards for wireless multimedia communication with high bit rate in the 5 GHz band are being developed in the US, Europe, and Japan. The available user data rate for these systems is supposed to be significantly greater than 10 Mbps. The high data rate and the channel characteristics are the main challenges for the design of the physical layer and in particular the selection of modulation technique for such a system. In this paper two modulation techniques, single-carrier and multicarrier modulation (implemented by OFDM), are considered as candidates. Both techniques are introduced, individually optimized to some extent and finally compared with regard to link performance and other aspects like coverage and power consumption. It is shown that for the assumed conditions the addressed coherent OFDM scheme provides about 2-3 dB performance gain compared to single-carrier modulation as well as non-coherent OFDM.

Comparison of attractive modulation schemes for the uplink in DS-CDMA systems

Several modulation schemes combined with convolutional coding which are attractive for the uplink in DS-CDMA systems are compared based on the criterion of maximum power efficiency. It is shown for typical system assumptions that 2PSK either with pilot channel or with pilot symbols time-multiplexed with data symbols, and 64-ary orthogonal modulation combined with coherent demodulation lead to the highest power efficiency. If the receiver complexity is taken into account, the conclusion is that 2PSK is the most suitable modulation scheme for the uplink in typical DS-CDMA systems.

Parameter optimization for decision directed frequency tracking for coherent OFDM

In wireless transmission systems frequency offsets have to be taken care off. OFDM showing otherwise good characteristics in mobile communication reacts sensitively to these offsets. In case of coherent modulation the situation is even worse as here-additionally to the fact that the offsets destroy the orthogonality of the subcarriers-the correct reception of long data frames is impossible due to the rotation of the signal constellation. Frequency tracking is therefore a necessity. This paper enlightens the context of a low-complexity PLL tracking structure for frequency selective transmission environments and shows that when exploiting this knowledge in an analytical optimization a significant improvement of performance and possibly a reduction in complexity can be achieved.

Concatenated coded spreading with coherent demodulation for DS-CDMA

In DS-CDMA systems, spreading may be viewed as inner coding and user-specific scrambling. In practice, spreading is combined with an outer convolutional code, which leads to so-called concatenated coded spreading (CCS). The standard approach is to use repetition codes. In the IS-95 uplink, a (64,6,32) orthogonal code is defined, which can be interpreted as 64-ary orthogonal modulation. In this paper, a CCS scheme with power efficiency superior to the IS-95 uplink is proposed. The use of decision-directed coherent demodulation for both schemes is discussed, and it will be shown that the coding gain of the improved CCS requires a modified channel estimation scheme.