Almost each year a new release of the UMTS standard was published. The first UMTS release in R99, finalized in 2000. In this section the main features of each release is presented.

i) Release R99: In this, UMTS Radio Access Network (UTRAN) was added in the circuit switched voice infrastructure and GPRS internet access. New network elements, Radio Network Controller (RNC) and The Node B are introduced in UTRAN. This release supports WCDMA with TDD and FDD modes of operation.

ii) Release 2000 or R00: This release specifies radio aspects, technical realization, codecs, end to end QoS messaging and data compression mechanisms. It supports GPRS/EDGE RAN and WCDMA RAN. It is further divided in to release 4 and 5.

Release 4: introduces new service architecture and QoS in fixed network. It also includes TD-SCDMA standard, UTRA-TDD. It also separates transport and control in IP based circuit switched domain.

Release 5: specifies all IP core network to integrate multimedia services without changing the air interfaces. For better audio quality 16KHz AMR codec is introduced. Each RNC is assigned to exactly one SGSN and each SGSN serves one or more RNCs.A High Speed Downlink Packet Access (HSDPA) up to 14Mbps peak data rate is also included.

iii) Release 6: It specifies High Speed Packet access (HSUPA) with uplink speed to 5.76 Mbps. It also supports use of Multiple Input Multiple Output (MIMO) antennas to enable multimedia broadcast and multicast services, security enhancements, interworking of UMTS and WLAN, IP based emergency call features and may more.

iv) Release 7: Further enhancements such as reduced latency, enhanced uplink performance, IP based multimedia services, emergency call handling, increased user throughput, increased peak data rate (100 Mbps downlink, 50 Mbps uplink), handover, and improvement for real time services are part of this release.

v) Release 8: Further it is intended to move towards all IP networks, integration of heterogeneous network types (WiMAX and WiFi) and access technologies (OFDMA for downlink and FDMA for uplink). It employs MIMO with up to 4 antennas per station. It also specifies channel coding scheme (Turbo coding) and contention free Quadratic Permutation Polynomial (QPP) turbo code interleaver.

vi) Release 9: It specifies high speed OFDM Packet access, which is viewed as 4G technology based on OFDMA radio to support 50 Mbps on uplink and 100 Mbps on down link.

vii) Release 10: It specifies Long Term Evolution (LTE) advanced 4G, peak download rate of 1Gbps.