Multiple access communications in future-generation wireless networks

In June 1971, the first two-way wireless transmission of data packets within a computer network was achieved at the Manoa campus, University of Hawaii, Honolulu [1]. The ALOHANet was an experimental UHF radio network designed and implemented at the University of Hawaii at a time when the only other option for remote access to information resources was based upon the use of inflexible, slow, and unreliable telephone network connections. The ALOHA System Research project began in September 1968, with the purpose of defining [2] “those situations where radio communications are preferable to conventional wire communications.” The properties of the wireless medium led to the use of a new form of random access channel architecture, now known as an ALOHA channel. The commercial application of ALOHA channels in the 1970s was limited by the fact that suitable frequencies for terrestrial wireless transmission of packets were not generally available. Thus, the first two commercial uses of an ALOHA channel were in cable networks and then in satellite networks. In 1973, Metcalfe demonstrated a cable-based application of ALOHA in the “Alto ALOHA Network” [3] at the Xerox Palo Alto Research Center. This network was later developed by Metcalfe into Ethernet. In 1976, an ALOHA channel was used for the request channel in the Marisat (later Inmarsat) satellite network [4]. Over the last 30 years millions of small two-way earth stations using ALOHA channels have been implemented around the world. In the early 1980s, frequencies for mobile networks became available [5] and in 1985 frequencies suitable for what became known as WiFi were allocated [6] in the USA. ALOHA channels were used in a limited way in the 1980s in 1G mobile phones for signaling and control purposes [7]. In the 1990s, Matti Makkonen and others at Telecom Finland greatly expanded the use of ALOHA channels in order to implement SMS message texting in 2G mobile phones. In the early 2000s, additional ALOHA channels were added to 2.5G and 3G mobile phones with the widespread introduction of GPRS using a slotted ALOHA random access channel combined with a version of the Reservation ALOHA scheme first analyzed by a group at BBN [8]. It seems clear that the expanding use of smartphones and IP-based web traffic in developing 4G networks will lead to an even greater use of random access ALOHA channels in this decade. Metcalfe at Xerox [9] and Kleinrock and Tobagi at UCLA [10] added the use of Carrier Sense (CS) and Carrier Detection (CD) to an unslotted ALOHA channel to define the CSMA/CD protocol used in the original Ethernet 802.3 cable standard. The 802.11 WiFi wireless standard modified the CD part of the Ethernet standard to Collision Avoidance (CA) to define the CSMA/CA protocols adopted in 1997 for WiFi. Ironically, recent chatter on the web dealing with full duplex WiFi hints at further development of WiFi in the direction of the original ALOHA architecture. The theoretical foundations of ALOHA random access have been described in various ALOHA System technical papers [11,12]. Over the last 30 years research groups throughout the world have provided a deeper, more complete understanding of the multiple access channel, its limitations, and its possibilities. Many of these possibilities are dealt with in this Special Issue of the EURASIP Journal of Wireless Communications and Networking. This Special Issue contains 21 selected articles, covering a significant number of hot topics in Multiple Access Communications such as new cooperative MAC protocols; spectrum sharing, and channel assignment techniques for cognitive radio networks; new results on PHY layer multiple access techniques; admission control, and radio resource management for multimedia traffic in WLANs, WIMAX, and LTE networks, as well as on general topics such as multiuser detection (MUD), cross layer, and quality of service. * Correspondence: [email protected] Department of Information and Communication Technologies, Universitat Pompeu Fabra, Spain Full list of author information is available at the end of the article Abramson et al. EURASIP Journal on Wireless Communications and Networking 2012, 2012:45 http://jwcn.eurasipjournals.com/content/2012/1/45