R ESEARCH working toward the specification of fourth-generation (4G) as well as " beyond third-generation " (B3G) wireless cellular systems is underway with the WRC Conference in 2007, the likely starting point for formal standardization. A key feature of 4G and B3G systems is likely to be the availability of significantly higher data rates than for third-generation (3G) systems. It has been suggested that data rates up to 100 Mb/s for high mobility and 1 Gb/s for low mobility should be target values. These data rates suggest higher spectral efficiencies and lower cost per bit will be key requirements for such future systems. It has been proposed that 4G should only have a cost per bit of 1/10 of that of 3G. Additional important expected features are likely to be increased flexibility of mobile terminals and networks, multimedia services , and high-speed data connections. Future convergence of digital audio and digital video broadcasting systems will clearly be another feature. Extensive use of multiple transmit and receive antennas for achieving radio links with increased reliability and spectral efficiency will probably also be a feature of such future systems. While a large number of papers on multi-input–multi-output (MIMO) systems have been published , much less attention has been paid to multiple-access schemes that would be able to efficiently share potentially high capacity of these systems among different users in an asynchronous channel. A number of activities are already taking place to upgrade existing 3G systems as evidenced in, for example, HSDPA, Super 3G, Integration with MediaFLO and DMB, Eureka 147 DAB and HIBOC DAB systems, as well as wireless LAN's 802.11 systems, WIMAX and WiBro. The papers in this issue are focused on state-of-the-art research on 4G wireless systems in radio access networks (RAN) up to layer 3, i.e., physical (PHY), medium access control (MAC), and radio resource control (RRC) layers. In our call for papers, we solicited papers covering a wide variety of issues including but not limited to the following topics: systems and architecture, interworking of networks, radio transmission technologies, wireless application protocols, multiple-access schemes, code-division multiple-access/time-division multiple-access/orthogonal frequency-division multiplexing access (CDMA/TDMA/OFDMA), software defined radio, multiple antennas and MIMO techniques, wireless multimedia audio and video, mobility management, resource allocation issues, bandwidth on demand issues, variable rate modulation and coding schemes, turbo codes and low-density parity-check (LDPC) codes, iterative decoding schemes, multiuser detection schemes, channel modeling and measurements, and convergence of …