Andreas Krämling

MAC protocols for wideband wireless local access: evolution toward wireless ATM

The wireless local area network (WLAN) and wireless ATM are emerging technologies for wideband wireless local access. Two standards, IEEE 802.11 and ETSI HIPERLAN type 1, are currently available for WLAN; the standardization process of wireless ATM, involving, among others, the wireless ATM Group of the ATM Forum and the broadband radio access networks project of the ETSI, is ongoing and related standards are expected to be released by mid-1999. This article focuses on the MAC protocol aspects of wireless local access networks. It first investigates, from a traffic performance point of view, the MAC protocol of the IEEE 802.11 and ETSI HIPERLAN type 1 standards, and then verifies to what extent these MAC protocols are suitable for wireless ATM. The analysis is then extended by considering a new MAC protocol, dynamic slot assignment (DSA++), which has been designed to explicitly support ATM technology over the radio interface. DSA++ is a candidate for the ETSI HIPERLAN type 2 standard, a developing ETSI standard for wireless ATM.

MAC protocol for wireless ATM: contention free versus contention based transmission of reservation requests

In general, the users of wireless ATM terminals request the same functionality and quality of service as users of wired terminals. These user requirements can be transformed into the demand for building an ATM multiplexer around the air interface which is characterized by a radio channel inside the ATM layer. The main difference between this logical ATM multiplexer around the air interface and a normal ATM multiplexer is the distribution of the multiplexing function between wireless terminals and the base station. For the uplink this requires a frequent notification of the ATM cell scheduler in the base station about the status of the incoming queues inside the wireless terminals. This paper focuses on different transmission methods for transmitting capacity request messages (also designated as reservation request) over the uplink.

Performance evaluation of a logical link control protocol for an ATM air interface

The paper deals with error control proceduresbased on repetitions necessary for an ATM air interface,which enables a full integration of wireless (W) ATMterminals into a fixed ATM network. The architecture and functionality of an additional LLC layer atthe air interface are explained. A set of ARQ protocolsfor the different ATM service classes is investigated.The protocol for VBR services is able to control the number of retransmissions depending on therequirements on maximum delay and residual cell lossratio. It also takes into account instantaneousconditions such as channel load from other sources.Furthermore, the protocol is able to discard ATM cells toavoid and resolve congestion. The performance of theprotocol has been evaluated by simulations.

Wireless ATM: Performance Evaluation of a DSA++ MAC Protocol with Fast Collision Resolution by a Probing Algorithm

In general, the users of wireless ATM terminalsrequest the same functionality and quality of service asusers of wired terminals. These user requirements can betransformed into the demand for building an ATM multiplexer around the air interfacewhich is characterized by a radio channel inside. Themain difference between this virtual ATM multiplexeraround the air interface and a fixed ATM multiplexer is the distribution of the multiplexingfunction between wireless terminals and the basestation. For the uplink this requires a frequentnotification of the ATM cell scheduler in the basestation about the status of the incoming buffers inside thewireless terminals. This paper focuses on differentmethods for transmitting capacity request messages (alsodesignated as reservation request) over theuplink.

Dynamic channel allocation in wireless ATM networks

During the last few years extensive research has been carried out to extend fixed ATM networks to mobile users. Currently the European Telecommunications Standards Institute (ETSI) is standardising new types of Broadband Radio Access Networks (BRAN): HIPERLAN/2 and HIPERACCESS. In cellular systems like HIPERLAN/2 the aspect of channel allocation plays an important role. In this paper two approaches for channel allocation are introduced and compared with each other concerning the spectrum efficiency and their influence on the implementation of wireless ATM networks and wireless LANs.

Interaction of power control and link adaptation for capacity enhancement and QoS assistance

Within this paper we present a new strategy for applying power control in combination with link adaptation in order to satisfy required quality of service (QoS) parameters and to possibly enhance the overall capacity of HIPERLAN/2 microcellular systems. The efficiency of our algorithm is then investigated and evaluated by means of simulations.

Point-to-multipoint ARQ protocol with efficient acknowledgement transmission

New ARQ protocols with spectral efficient acknowledgement and retransmission traffic for reliable point-to-multipoint communication are introduced. One key feature of the proposed algorithms is the simultaneous transmission of negative acknowledgements. In combination with adaptive antennas selective retransmission for broadcast traffic considering the radio channel conditions becomes possible. Performance results for the HIPERLAN/2 system show the benefit of the new algorithms.

Supporting cost efficient public 5 GHz-W-LAN roll out with a multihop HIPERLAN/2 concept

This contribution highlights the possibilities and service characteristics for a cost and time efficient roll out for public wireless local area networks providing wide coverage in urban areas. The HIPERLAN/2 (H/2) multihop concept is based on intermediate relay stations. This eliminates the need for intensive cabling, reducing the costs. The H/2 multihop concept introduces a new element called forwarding mobile terminal (FMT) to the H/2 world. The FMT is a modified H/2 mobile terminal which only needs different software, but no additional transceiver. In city scenarios, the forwarding concept allows a fast roll-out while limiting the cabling cost and providing a reasonable user service in a large service area.

Schnurlose Breitbandsysteme (Wireless ATM)

Als Breitbandsysteme sind allgemein solche Systeme anzusehen, die eine besonders hohe Ubertragungsrate ermoglichen. Die genaue Definition des Begriffes findet man in der ITU-T-Empfehlung 1.113. Hier werden Breitbanddienste dadurch charakterisiert, das die erforderliche Ubertragungsrate hoher als bei einem Primarmultiplexanschlus im ISDN (2048 kbit/s) ist.