Double-directional, ultra wideband dual-polarized channel measurements at 70 GHz have been carried out in a small-office environment. The aim of these measurements is to study the temporal, directional, and polarization properties of the channel for modelling purposes of the future wireless communication systems at mm-waves. A highly deterministic behaviour of the channel and the environment has been identified, as well as the limitations of only parameterizing channel models as WINNER for the new mm-wave channel models.

A wideband, fully polarimetric and directional radio channel sounding campaign conducted at 70 GHz is presented. Measurement site was chosen as an entrance hall, featuring femtocell size. Transmitter and receiver were placed according to an access-point scenario. Initial large-scale parameters like excess-delay, delay-spread and angular spread are derived for channel characterisation. It is not the paper's goal to describe a new channel model. The main focus is the identification of propagation effects and characteristics, which have to be considered in future modelling. It was found, that first more specular than diffuse components occur and second the channel is spatially sparse.

Owing to the limitation in bandwidth of currently used frequency bands, future fifth generation (5G) mobile networks will need to operate at higher frequencies. However, one important step in the research activities for the next generation of mobile networks is the broadband fully polarimetric analysis of the multipath propagation in dynamic single and multiuser scenarios under time-variant shadowing environments in millimetre- wave (mm-wave) channels. This paper presents a channel sounding campaign at 70 GHz in an urban outdoor scenario focusing on broadband channel characteristic at mmwave. For the measurements a novel dual-polarized (DP) ultrawideband (UWB) multi-channel sounder (DP-UMCS) architecture, developed at the TU Ilmenau for propagation measurements in cellular networks, was used to study the directional and polarization properties of the channel in view of the future wireless communication systems.

The Machine-type services induce one critical challenge for the current cellular networks: The capacity of the conventional signaling channel in the network can hardly support the anticipated massive number of machine-type devices. According to the current network design, the signaling channel can easily be blocked up by a number of simultaneous signaling requests. In order to release the bottleneck of the signaling channel, we proposed a cross-device signaling mechanism to reduce the transmitted signaling data during the congestion-critical period. This mechanism removes the redundancy between the signaling messages of different devices. It has especially high performance when multiple highly synchronized devices generate simultaneous signaling requests. Thus, the mechanism can effectively mitigate the potential congestion in the signaling channel and further increase the design capacity of the network.

Relay deployments promise to alleviate the limitations of conventional macrocell networks, such as poor indoor penetration and coverage holes in a cost-efficient way. In this context, the capacity of the wireless relay link between a relay node (RN) and its serving base station (BS) has a crucial role in the achievable end-to-end performance. The deployment flexibility of RNs, which mainly stems from the wireless relay link, compact physical characteristics, and low-power consumption, can be exploited by relay site planning (RSP) to overcome the limitations of the relay link and, thus, enhance the system performance. To this end, RSP is carried out via selecting an RN deployment location from a discrete set of alternatives considering the signal-to-interference-plus-noise ratio (SINR) on the relay link as the selection criterion. In practice, the so-called coarse RSP takes into account only large-scale fading due to shadowing. Nevertheless, as RNs are stationary, the wireless channels pertaining to relay deployments are subject to simultaneous impairments by both shadowing and multi-path fading, i.e., composite fading/shadowing. In this paper, we present the performance of coarse RSP that can be used for planning and dimensioning of two-hop cellular relay networks in composite fading/shadowing environments, where co-channel interference is also present. The relay link is modeled by Nakagami-lognormal distribution while the access link between a mobile terminal (MT) and its serving RN is modeled by Rician-lognormal distribution. Furthermore, we provide an accurate analytical framework through closed-form expressions for relay link SINR, link rates, and end-to-end rate. Results show that coarse RSP can still yield high performance improvements considering composite fading/shadowing channels.

In next generation systems and networks, the incorporation of mechanisms achieving robust, predictable and self-adaptive behavior with minimum cost will be a key requirement. Towards this goal we introduce the notion of the "self-growing network". The latter, in its initial deployment stage, is limited to a single dedicated purpose (energy-efficient networking, spectrum efficient communications, control and surveillance use, etc) but can evolve/grow into a multi-purpose, versatile infrastructure, that serves a broader range of applications by utilising combinations of self-x and cooperating features.

A new method for spectrum sharing for a single operator is presented. One operator with its frequency band divided into three bands is assumed: one central band for the TDD mode and two more in the sides for the up and downlink of the FDD mode. The idea is to share resources between these bands, when required. Two different approaches are proposed: block-wise sharing approach, where a fixed block of frequencies can belong to either TDD or FDD, depending on the necessities; and tunable carrier frequency approach, where the exact bandwidth to be transferred is previously calculated. The fresh results give the industry and regulatory bodies a good reference for spectrum management schemes towards future IMT-A systems.

Future cellular wireless networks based on MIMO-OFDM enable high data rates in outdoor scenarios. Limitations in coverage, especially at cell-edge, might be overcome by transmission over relays, which is therefore widely discussed for LTE-advanced networks. Here, a multi-hop relay node is placed at the cell-edge or in a coverage hole in order to compensate for the penetration path loss caused by buildings. Relay nodes can be deployed in two modes, either as amplify and forward or as decode and forward relay. The later system may benefit from independent link adaptation which is a key concept especially under fading conditions in outdoor broadband wireless. This paper reports on first multi-hop relaying field trials in the LTE downlink. These field trials were carried out in a single-cell, single sector urban outdoor environment within the Berlin LTE-advanced testbed. Results show that outdoor relaying is a key concept to deliver high data rates to the cell edge. Furthermore, results show that rates above 60 Mbps are achievable and outdoor relaying yields for a 300 m range extension. In addition, results show that multi-hop relaying provides cell-edge users with a minimum data rate of at least 20 Mbps which is mandatory, especially if QoS constraints have to be met.

With rapid growth of mobile users and developents of mobile equipments like cell phones, laptops and personal digits assistances (PDA), mobile networks have to meet dramatically increased service demands in the nearest future. The ever-increasing demands, such as the users expect to enjoy the service anywhere, anytime and the networks support a seamless mobility, driving the evolution of mobile networks at a fast pace. The next generation mobile network (LTE in 3GPP) is conducting research towards this goal. An IP protocol based flatter network architecture has been introduced in the next generation mobile networks (NGMN). In this network architecture, gateway (GW) is the only node which establishes a connection between RAN and external world. To provide capabilities of gateways catering for service demand at different stages, more advanced functions such as load balancing between gateways is proposed. Such mechanism will be used as a solution to avoid gateways congestion and optimize network performance for the future network. In this paper, based on the described flat architecture of the next generation mobile networks and some related concepts such as the pool of gateway, inter-GW load balancing approach has been introduced followed by performance evaluation. Simulation results show promising gains provided by the inter-GW load balancing mechanism for next generation systems.

The use of relay stations in the cellular network is a good candidate method to enhance the cell edge data rate, and to provide homogeneous QoS experience for users in different locations. We discuss the decode-and-forward type relay station within the context of the 3GPP RLC/MAC layers. The emphasis is on proper RLC layer operation for the relay-enhanced-cell (REC). RLC layer evolvement in the future high data rate radio access network will first be discussed, then its performance in REC will be investigated, with or without it being implemented on the relay station. Simulations are conducted on the downlink for the future OFDMA-based relay network, from which we finally draw significant conclusions.

In this paper, we present real-time broadband multi-user multi-antenna measurements in typical indoor and outdoor scenarios. For the first time, essential frequency-selective functions of a new medium access control (MAC) layer, namely fair resource assignment to multiple users, spatial mode selection and adaptive modulation, have been implemented in real-time on standard digital signal processing hardware. The new MAC layer is steered over wireless feedback and control channels in a closed loop manner. Our implementation uses parameters close to the forthcoming long-term evolution (LTE) of the 3G air interface, thus illustrating the feasibility of the new functions in next-generation cellular radio systems. The paper describes our real-time implementation and reports several test results. Benefits of the frequency-selective multi-user MIMO MAC are validated in realistic mobile propagation environments.

Relay enhanced cellular network is a promising architecture for next generation wireless communication system. Introducing relay nodes into cellular networks challenges the resource allocation. The centralized subcarrier and power allocation algorithm which maximizes system capacity with constraint of overall transmission power is studied for OFDMA based relay enhanced cellular networks. A heuristic algorithm is proposed for subcarrier assignment to exploit multiuser diversity as much as possible. An iterative power allocation algorithm is presented to balance the two-hop links of each relay node based on the predetermined subcarrier assignment solution. Performance of the proposed algorithms is evaluated. Numerical results show that the proposals can achieve significant improvement on system capacity without heavy computational complexity.

Digital relaying is a promising technique to improve the signal quality in the future wireless network. A scheme of two-hop cellular network with fixed relay nodes (FRN) is investigated in this paper. Based on this scheme, signal to interference ratio (SIR) received by base station (BS) and FRN are analyzed. Theoretical analysis and simulation results show that the SIR and system spectral efficiency can be improved significantly when FRNs are employed in cellular system. We also show that the antenna height of FRN and the cell radius of BS and that of FRN influence SIR received by BS and FRN and the system spectral efficiency greatly. The proper antenna height of FRN and cell radius of BS and that of FRN are also given in this paper. Finally, the problems with current frequency planning are discussed.

This paper addresses aspects of radio resource management of a cellular network enhanced with two-hop fixed relay nodes (FRNs). The network is assumed to be working in the half-duplex FDD mode and have synchronized downlinks. To effectively manage the inter-cell interference, a reuse partitioning based resource partitioning framework is proposed. Under this framework, we develop a channel-aware intra-cell resource assignment scheme. According to this scheme, the available time-frequency resources are assigned, with the aid of channel-dependent user partitioning, in the way that can effectively increase cell capacity. It is demonstrated through intensive computer simulations that with our scheme the FRN enhanced network can remarkably outperform the conventional network without relaying. The performance superiority of our scheme over a known resource partitioning scheme for FRN enhanced network is reported as well.

Relay enhanced cellular network has been proposed as a promising solution for the next generation wireless system. Based on an appropriate frame structure for such OFDMA based relay network, round-robin algorithm is extended as a performance benchmark. Two special algorithms (greedy polling and partial proportional fair) are proposed for adaptive resource scheduling. Throughput results of simulations show that the proposed adaptive algorithms can achieve significant improvement on system performance and the relay enhanced cellular network outperforms the traditional network significantly for supplying high data rate for users at the cell's edge. The results of jitter's deviation indicate greedy polling algorithm is applicable to realtime service and partial proportional fair algorithm is suitable for non-realtime service.

This paper investigates the issue of frequency planning for cellular systems enhanced with two-hop fixed relay nodes (FRNs) under the assumption of frequency reuse one. A channel dependent intra-cell spectrum partitioning solution is proposed. According to this solution, the mean values of the signal-to-interference-ratio on respective sets of links are taken into account to determine the bandwidths assigned to base station (BS)-FRN links, FRN-mobile terminal (MT) links and BS-MT links. Moreover, by combining above intra-cell spectrum partitioning solution with different inter-cell interference management approaches, we propose three concrete frequency planning schemes, i.e. the cell-partitioning based scheme, the virtual-sector based scheme and the virtual sector enhanced cell-partitioning based scheme. It is shown through computer simulations that the FRN enhanced cellular systems with proposed frequency planning schemes can remarkably outperform conventional cellular systems when FRNs are communicating with BS over line-of-sight (LOS) links. The proper positioning of FRNs and the impacts of the reliability on the BS-FRN links are addressed as well.

To improve the spectral efficiency and to control inter-cell interference effectively, this paper proposes a joint routing and resource partitioning scheme for cellular network enhanced with two-hop fixed relay nodes. A new reuse partitioning based framework is adopted firstly to facilitate efficient radio resource partitioning, which enables aggressive frequency reuse. Then, a channel-dependent routing scheme is proposed, which aims to maximize cell capacity under the constraint imposed by the resource partitioning framework. Intensive computer simulation results demonstrate the performance superiority of our proposed scheme to several known routing and resource allocation schemes. Issues of FRN positioning and radiation power are also investigated.

We investigate channel estimation for timeslot-structured single-carrier block transmission (SCBT) over space-, time-, and frequency-selective fading multiple-input multiple-output (MIMO) channels. A MIMO-SCBT with a dual cyclic timeslot structure is presented first. Then, an optimal channel estimation in the minimal mean square error (MMSE) sense on the timeslot basis is investigated. It is shown that the optimal pilots for the timeslot-based MMSE channel estimation are related to the statistical channel state information in eigenmode. Under the assumption that the transmit correlation is unknown at the transmitter, the optimal pilots satisfy the same condition as reported for the block-based least-square (LS) channel estimation in literature, and the channel estimation can be simplified to initial block-based LS channel estimation followed by space-time postprocessing. Particularly, for spatially uncorrelated channels, the space-time postprocessing can be reduced to pathwise processing. A new design of the pilot sequences is given, which leads to an efficient implementation of the channel estimation. Later on, a more efficient implementation for the initial channel estimation is obtained by using the structure of the pilot sequences, and discrete cosine transform (DCT)-based implementation is developed for the space-time postprocessing to approximate the optimal solution with low implementation complexity. Finally, the performance of the proposed channel estimation is verified via simulations.

Following the principle of reuse partitioning, this paper proposes two new frequency planning schemes for cellular system with two-hop fixed relay nodes (FRNs). The coverage-oriented scheme is developed with emphasis put on the signal to interference ratio (SIR) experienced by mobile terminals within whole coverage area, while the efficiency-oriented scheme is developed targeting at a higher spectral efficiency. Taking uplink as an example, both simplified analysis and intensive computer simulations are presented to offer comparison among FRN enhanced systems with our proposed schemes, that with a known channel-borrowing based frequency planning scheme and the conventional cellular system without relaying. Our studies show that the FRN enhanced system with our coverage-oriented scheme provides the largest worst-case SIR, while that with our efficiency-oriented scheme offers a remarkably higher spectral efficiency

In order to reduce the signaling overhead in adaptive OFDM transmission systems being designed for B3G and 4G wireless communications, the basic resource unit, referred to as chunk, comprises a number of adjacent sub-carriers and OFDM symbol periods. A consequent open issue is the mapping of long codewords onto limited size chunks, especially when link adaptation per chunk is carried out. This paper proposes a new method for joint coding and modulation. A data packet, independently of its length, is encoded without any segmentation into a single codeword spanning different chunks employing different signal constellations. The parameters of the underlying error correction code are chosen independently of the signal constellation and no puncturing is required. Moreover, a joint adaptation of the code length and the modulation format is proposed to optimise the number of chunks allocated for transmission

In this paper, we present a game-theoretical approach to allocate the power in multicell OFDM systems by a distributed way. A specific utility function is defined considering the users' average utility per power, i.e., power unit based utility. The resource control problem is formulated as a noncooperative game, with which the properties of the Nash equilibrium of the game is investigated. Since the equilibrium is Pareto inefficient, we propose a pricing policy to the user's transmit power by adding a penalty price. With the adoption of the price, the user's aggressive behavior is depressed and Pareto improvement is achieved. Simulation results show that the proposal outperforms the pure water-filling algorithm and the users obtain higher utility and lower transmit power by proper pricing policy

This paper investigates the issue of frequency planning for cellular system enhanced with two-hop fixed relay nodes (FRNs). Unlike most papers focused on FRN enhanced cellular system, we assume that there is no performance enhancing techniques deployed on the BS-FRNs links. In particular, we propose two frequency planning schemes following the principle of reuse partitioning, and compare, under the assumption that BS communicates with FRNs via non-line-of-sight (NLOS) links, the system performance between our schemes, the case when the channel-borrowing based frequency planning scheme in [4] is employed, and the conventional system without relaying. It is demonstrated that our proposed schemes can improve the quality of service for mobile terminals located near cell boundaries and can provide remarkably better performance over the frequency planning in [4]. Our studies also show that to fully exploit the potentials of FRN enhanced cellular system some performance enhancing techniques on the BS-FRNs links seem to be indispensable.

Radio resource allocation is important in the relay enhanced cellular network. Some smart radio resource allocation schemes have been proposed, such as the "pre-configured and fixed" scheme (H. Hu et al., 2004). In this paper, we propose a new scheme by introducing reuse partitioning into the cellular network with fixed two-hop relay nodes. Theoretical analysis and simulation results show that, in comparison with the conventional cellular network and the scheme proposed in H. Hu et al., (2004), our scheme not only improves the system capacity, but also provides better QoS (quality of service) for users located near cell edges. Moreover, since in our scheme resources are dynamically allocated among relay nodes, more benefits can be obtained under the non-uniform traffic distribution in comparison with the scheme in H. Hu et al., (2004), of which the resources are allocated in a fixed way

This paper studies the reverse link power saving characteristic of relay enhanced cellular network, in which the relays are placed at fixed locations and each wireless route includes at most one relay. Results of theoretical analysis and intensive computer simulation have proved that, under the same demand of wireless link qualities as the conventional cellular network, the necessary transmission powers of mobile terminals can be significantly saved even if the relays share the radio resources of the conventional network.

MIMO systems can offer high multiplexing and diversity gain, but the increased complexity hampers the practical applications. Through antenna selection, the complexity and cost can be greatly reduced while the gain of MIMO systems can be reserved. In this paper, a fast sub-optimal antenna selection algorithm based on norm and correlation is proposed for maximizing the channel capacity. Compared with the near-optimal selection algorithm of M. Gharavi-Alkhansari and A. Greshman (2004), our sub-optimal algorithm can capture most of the capacity property while the complexity and memory requirement are greatly decreased. Simulation results show that our algorithm is very effective when SNR is high and the number of the selected antennas is relatively small. Especially for a rank deficient channel matrix, the sub-optimal algorithm outperforms the norm-based selection algorithm. Our algorithm also shows capacity advantages when compared with the correlation based method (CBM) algorithm of Y.S. Choi et al. (2003)

This paper proposes a new cellular network architecture that simultaneously employs reuse partitioning and fixed relay nodes. Several key issues of the proposed architecture, e.g., the placing positions of relay nodes and the assignments of available carriers, are addressed with theoretic analysis and computer simulations. Our studies show that in comparison with the conventional cellular network our proposed scheme not only improves the system capacity, but also provides better quality of service (QoS) for users located at cell edges

In this paper, an efficient digital implementation of multicarrier transmission scheme based on generalized discrete Fourier transform (DFT) filter banks is presented for multicarrier code-division multiple-access (MC-CDMA) systems. Generalized DFT filter banks has been traditionally discussed for very high-speed digital subscriber lines (VDSL) wireline systems, received interest also for wireless applications. The design of the generalized DFT modulated filter banks is investigated and its fast implementation is derived in the time-domain for arbitrary integer sampling rate. Through the utilization of the generalized DFT modulated filter banks, one or more subcarriers, even noncontiguous subcarriers can be easily supported by system in both uplink and downlink, which facilitates the users to access the network in a frequency-division multiple-access manner. Simulation results show that the overall bit-error-rate performance of the proposed multicarrier transmission scheme well approaches that of a single-carrier system due to the negligible intercarrier interference introduced by an appropriate design of the generalized DFT modulated filter banks.

We present a multi-antenna real-time implementation of a cross-layer uplink scheduler based on a recently developed framework. We outline the theory behind the stability-optimal scheduler, which achieves the entire stability region of the multiple access channel. We discuss the trade-off between theoretical optimality and real-time operation under real-world constraints, which leads to the development of an efficient fair scheduler. Finally, we evaluate the performance of the fair scheduler in experimental measurements (on state-of-the-art hardware) in a typical office scenario, which shows an increase in spectral efficiency and the possibility to guarantee a certain link quality of service threshold.

The interleaved frequency division multiple access (IFDMA) scheme is based on compression, repetition and subsequent user dependent frequency shift of a modulated signal. Multiple access is enabled by the assignment of overlapping but mutually orthogonal subcarriers to each user. In this paper it is shown that IFDMA can be regarded as unitary precoded OFDMA with interleaved subcarriers. On the other hand, IFDMA is shown to be a CDMA variant with frequency domain orthogonal signature sequences and chip interleaving. Thus, it combines the advantages of single and multi-carrier transmission such as low peak to average power ratio, orthogonality of the signals of different users even for transmission over a time dispersive channel and low complexity. Simulation results show the good performance of coded IFDMA transmission over a mobile radio channel for different data rates

The interleaved frequency division multiple access (IFDMA) scheme is a promising candidate for next generation mobile radio systems. IFDMA is based on compression, repetition and subsequent user dependent frequency shift of a modulated signal. As in OFDMA, multiple access is enabled by the assignment of overlapping but mutually orthogonal subcarriers to each user. It combines the advantages of single and multicarrier transmission such as low peak to average power ratio, orthogonality of the signals of different users even for transmission over a time dispersive channel and low complexity. In this paper, a linear low complexity frequency domain equalizer for IFDMA is presented and extended by subsequent decision feedback with initialization. Simulation results show the good performance for data transmission using IFDMA with frequency domain equalization over a mobile radio channel

The Doppler shift of the time-varying multi-path channel is estimated by calculating the level crossing rate (LCR) of the signal envelope of the channel coefficient estimates of the strongest path. In order to reduce long observation duration and memory requirements, we recommend to use the 1st order autoregressive (AR(1)) filter. Simulation results show the fast convergence of the proposed algorithm while guaranteeing the estimating accuracy at the same time.

This work proposes an adaptive antenna tilting approach in an overlay UMTS FDD network. The purpose is to introduce and investigate an antenna element, which can be remotely controlled by the radio network, in order to adequately cater for the spatial and temporal dynamic traffic distributions. The tilting angle is computed by a two level control mechanism: the higher level is controlled by the network manager and consists of a look-up table with the possible ranges (intervals or discrete steps for angles) of the antenna angle adjustments. The element manager, e.g. RNC controlling and recording the track of the dynamic antenna changes, controls the lower level. To enhance the system reliability, we associate the less dynamic traffic with the primary fixed tilt antenna, whereas the more varying traffic is controlled by a second more dynamically tilted antenna element. Through system level simulations, we show that significant gains in term of system capacity can be obtained. In addition, solutions involving the network management subsystem in UMTS FDD are also given, where the element management platform interacts with the performance measurement units. Intelligent inter-frequency handovers are deliberately discussed.

Multi carrier (MC) transmission is considered the leading candidate for a new air interface for fourth generation wireless systems. In order to enable a flexible exploitation of the envisaged large transmission bandwidths, a sub-division of the available bandwidth into sub-bands through FDMA (frequency division multiple access) is seen as a very promising solution. Within each sub-band, an MC-multiple access system can be accommodated. Recently, an efficient adaptive sub-band allocation (ASBA) approach has been shown to provide a significant performance gain in such systems. A system design method is proposed that yields, for each propagation scenario, the proper number of sub-bands, such that a given performance gain can be attained through ASBA.

The radio resource scheduling algorithms and power distribution strategies for multi-user MIMO mobile communications system are investigated. The performances of different power distribution strategies combined with diverse scheduling algorithms are compared for the consideration of system capacity and QoS guarantee. Numerical results show that the combination of dynamic scheduling and water-filling solution can enhance system capacity and reduce packet-discarding ratio.

In this paper, a coding scheme with M-ary Walsh-Hadamard (WH) orthogonal modulation is considered for multi-carrier (MC) transmission. A novel pilot-assisted channel estimation approach is proposed, that efficiently exploits the properties of WH codes. Firstly, simulation results on the single-user performance show the influence of the energy distribution between pilot and information symbols. Then, the impact of the channel estimation method is assessed for different system loads in a MC code division multiple access (MC-CDMA) uplink scenario.

Multi-carrier (MC) transmission is seen as the leading candidate for beyond 3G mobile communications. We focus here on the MC scheme known as filtered multi tone (FMT) modulation. We investigate its suitability for an asynchronous uplink multi-user scenario, under the hypothesis of frequency division multiple access (FDMA). In particular, we show the influence of the filter spectral characteristics and the effects of introducing some redundancy in bandwidth through non-critical sampling. Furthermore, we compare the achievable performance with that of an OFDMA system over an AWGN channel in terms of bit error rate.

UMTS Terrestrial Radio Access (UTRA) in time division duplex (TDD) mode is a combination of time division multiple access (TDMA) and code division multiple access (CDMA). Radio resources are disposed in the time as well as in the code domain and allow a variable allocation to either uplink or downlink transmission. With this characteristic, UTRA-TDD allows to flexibly adapt the physical channel and radio frame structure to various kinds of services in different environments and traffic conditions. Depending on the choice of radio resource management (RRM) algorithms, this paper focuses on simulative capacity estimation in a typical micro-cellular dense urban environment with a service mix of speech and Internet data traffic.

A novel data multiplexing scheme is presented. This technique uses an antenna array with K transmit antennas. In. total K information bits are multiplexed in an orthogonal fashion. The special property of the multiplexing technique is that, for each symbol duration, only one out of K antennas is transmitting using BPSK modulation. Furthermore, the symbol duration is equivalent to the bit-duration due to the parallelism introduced by the K antennas. The receiver is able to detect the transmitting antenna and by using this information the demultiplexing is carried out. It is demonstrated that the proposed method achieves about the same spectral efficiency as 8PSK, but with a relaxed bit-energy-to-noise ratio of about 2.5 dB. Furthermore, the linear channel capacity gain (error-free transmitted bits) over the single antenna BPSK transmission scheme is found to be in the range of 2.5-3.

Cellular networks and wireless local area networks (WLAN) are being widely deployed for mobile radio communications. Taking into account the advantageous and drawbacks of both network architectures, it becomes obvious that a combination of them is the logical consequence for future mobile radio networks. The scope of this paper is to introduce a future radio network architecture called hierarchical multihop cellular network (HMCN), which includes several multihop cells. The overlaying cellular network coordinates multihop cells in order to reach an optimal load balance in the whole network. The next evolutionary step towards a HMCN structure is to introduce multihop capable nodes (MHN), which can be fixed or even mobile. The paper shows the challenges and benefits of multihop with fixed nodes, especially the placement of fixed MHN and reduction of radio protocol overhead in order to provide high performance. When MHN are normal mobile nodes, multihop routing becomes a key point in the HMCN concept. The paper proposes a cellular based routing scheme and compares it with the ad hoc routing algorithms being developed by IETF.

The paper defines a radio resource management concept for multimedia services in future broadband mobile radio networks. Based on the HIPERLAN/2 system, we design an adaptive radio resource scheduler which autonomously adapts to current traffic types and volume. We assume IP traffic models for voice, HTTP and video users and optimize the scheduling functions in the access point (base station) of the broadband mobile network in order to maintain QoS for the services. The interworking among admission control, load control and the adaptive scheduler is shown. The principles discussed here are not restricted to H/2 but can be exploited for any radio access technique (RAT) using adaptive schedulers, e.g. dynamic scheduling for reconfigurable terminals.

The goal of the FleetNet project is to develop an air-interface for inter-car communication and road telematics. For the raido interface, the framework of the UMTS Terrrestrial Radio Access Time Division Duplex (UTRA TDD) air-interface shall be used with modifications. This paper introduces a concept for the air-interface, highlights the challenges for its use in an ad hoc network with rapidly changing topology and offers a description as well as an evaluation of the required changes within the medium access control and radio resource management layer