uces an additional set of ETSI deliverables (and maintenance thereafter) in order to enhance TETRA in accordance with the following requirements: (a) Evolution of TETRA to provide packet data at much higher speeds than are available in the current standard. This is to support multimedia and other high speed data applications required by existing and future TETRA users. (b) Selection and standardisation of additional speech codec(s) for TETRA, to enable intercommuni- cation between TETRA and other 3G networks without transcoding and to provide enhanced voice quality for TETRA by using the latest low bit rate voice codec technology. (c) Further enhancements of the TETRA air interface standard in order to provide increased benefits and optimisation in terms of spectrum efficiency, network capacity, system performance, quality of service, size and cost of terminals, battery life and other relevant parameters. (d) Production and/or adoption of standard to provide improved interworking and roaming between TETRA and public mobile networks such as GSM, GPRS and UMTS. (e) Evolution of the TETRA SIM, with the aim of convergence with USIM, to meet the needs for TETRA specific services while gaining the benefits of interworking and roaming with public mobile networks such as GSM, GPRS and UMTS. Extension of the operating range of TETRA, to provide increased coverage and low cost deployments for applications such as airborne public safety, maritime, rural telephony and 'linear utilities' (e.g. pipelines). (g) Provision of new ETSI deliverables in order to support further user/market-driven requirements that may be identified during study work in the early stages of the work programme. Ensure full backward compatibility and integration of the new services with existing TETRA stan- dards, in order to provide future proof of existing and future investments by TETRA users. TETRA standards are freely available from ETSI. The following list includes the major standard series of TETRA voice plus data (V + D) and direct mode operatio