Monday, June 28, 2010

Classification and development of LTE standard

Standards may arise from different processes and an useful distinction can be made between formal (de jure) standards and de facto standards. Formal standards includes mandatory standards, which are promulgated by government agencies with regulatory authority, and voluntary standards, which are developed by international, regional or national standards organizations, broadly known as Formal Standardization Organizations (FSOs). De facto standards, on the other hand, emerge from market processes and are developed by individual companies or by industry trade associations or consortia.

LTE standard is a voluntary formal standard developed by the 3rd Generation Partnership Project (3GPP). 3GPP is a collaboration agreement that was established and formalized in December 1998 and that brings together a number of regional and national telecommunication standardization bodies of Europe, USA, China, Japan, and Korea. A detail description of the 3GPP Standardization Body including its members, scope and structure is given in a dedicated post along with a description of the 3GPP support organizations, i.e. NGMN (alliance of service providers and activities sponsored by vendors) and LSTI (an initiative of all types of stakeholders to trial the technology).

Open standard or proprietary standard?

There are several definitions of open standards which emphasize different aspects of openness, including the openness of the resulting specification, the openness of the drafting process, and the ownership of rights in the standard. According to the general definition, open standards are those considered to have diffused widely and been adopted by most companies in the market. The companies using them are not required to pay for the right to manufacture products in accordance with the standard, other than nominal fees (if any) imposed by the FSOs. Proprietary standards, on the other hand, are controlled by a single company or by a handful of companies and are protected by Intellectually Property Right (IPR). Other companies are required to pay for the rights to use these standards.

Being a formal standard, the standardization process of LTE is characterized by openness, due process, and consensus, which assume fairness and equity among participants. Anyway, the intellectual property and patents of contributors of the standard impact the openness of the standard. In the following we will analyze the openness of the LTE standard through the requirements that make a standard open defined by Krechmer in 2006:

  1. Open Meeting: participation is open in various technical specification groups (TSG) and working groups (WG) to all members of 3GPP;
  2. Consensus: 3GPP’s project co-ordination group (PCG) and technical specification groups (TSG) endeavor to reach consensus on all issues;
  3. Due Process: 3GPP’s PCG, TSG, and WG have mandate to handle appeal process from individual members;
  4. Open IPR: members are required to declare their IPRs that are essential and grant licenses on fair terms, reasonable terms and conditions, and on a non-discriminatory basis;
  5. One World: 3GPP standards are applicable worldwide;
  6. Open Change: all changes and proposals are discussed in TGS and WG, and become enforced after consensus;
  7. Open Documents: 3GPP specifications and reports are available without any charges to all;
  8. Open Interface: specifies and sets open interfaces for various components of a wireless system;
  9. Open Access: interoperability, accessibility, and safety aspects are handled in the specifications and reports;
  10. On-going Support: 3GPP standards are evolving continuously release over release.

Note that 3GPP LTE fulfills all the Krechmer’s requirements except for “Open IPR” which is fulfilled only in part. Indeed, the intellectual property, instead of being available on a royalty-free basis, have to be licensed to all applicants on fair terms and conditions and on a non-discriminatory basis. LTE technology IPR is owned by various companies involved in the technology development and their collaboration via the NGMN and LSTI alliances enabled them to agree on low royalty for IPR licenses to each other. This is unlike CDMA technology where IPRs were mostly owned by a single company (i.e Qualcomm). Moreover, the rules for standards published by the major internationally recognized standards bodies such as the IETF, and ITU-T allow an open standard to contain specifications whose implementation require payment of reasonable and non-discriminatory patent licensing fees. Therefore, it can be concluded that 3GPP LTE is considered to be an open standard.

LTE standard development stages

The 3GPP work on the Evolution of the 3G Mobile System started with the RAN Evolution Work Shop, 2-3 November 2004 in Toronto, Canada. The Work Shop was open to all interested organizations, members and non members of 3GPP. Operators, manufacturers and research institutes presented more than 40 contributions with views and proposals on the evolution of the Universal Terrestrial Radio Access Network (UTRAN). A set of high level requirements was identified in the Work Shop:

  • Reduced cost per bit
  • Increased service provisioning
  • more services at lower cost with better user experience
  • Flexibility of use of existing and new frequency bands
  • Simplified architecture
  • Open interfaces
  • Allow for reasonable terminal power consumption

It was also recommended that the Evolved UTRAN should bring significant improvements to justify the standardization effort and it should avoid unnecessary options. With the conclusions of this Work Shop and with broad support from 3GPP members, a feasibility study on the UTRA & UTRAN Long Term Evolution was started in December 2004. The objective was “to develop a framework for the evolution of the 3GPP radio-access technology towards a high-data-rate, low-latency and packet-optimized radio-access technology”.

In september 2005 the feasibility study resulted in the first stage of the HSPA+ (Evolved High Speed Packet Access) Standard. HSPA+ represents the first step towards LTE, indeed, it increases the downlink/uplink data rate and reduces the latency in respect to HSDPA/HSUPA, and introduce MIMO technologies along with higher order modulation (64QAM). As further step towards LTE, it specifies an optional all IP-base architecture. 3GPP synchronizes specification development into releases and HSPA+ corresponds to the 3GPP Release 7.

In December 2008 the first release of the LTE Standard, namely 3GPP Release 8, was completed. It includes more than 1000 specifications divided in series with numbers from 21 to 36. For instance, in the following we report some specifications that we have used as reference for the Introduction of this blog and for other previous works:

  • TR 25.913 collects the Requirements of the Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN);
  • TS 33.400 series describe the Security Architecture;
  • TS 36.200 series describes the Physical layer specifications of E-UTRA: General description (TS 36.201), Physical channel and modulation (TS 36.211), Multiplexing and channel coding (TS 36.212), Physical layer procedures (TS 36.213), Physical layer measurements (TS 36.214);
  • TS 36.300 series describe the Layer 2 specifications of E-UTRA: Medium Access Control (MAC) protocol specification (TS 36.321), Radio Link Control (RTL) protocol specification (TS 36.322), Packet Data Convergence Protocol (PDCP) specification (TS 36.323), etc.;
  • TS 36.400 series describes the E-UTRAN architecture.

Providing a detailed list of specifications is far from the goal of this blog, but to a determinate and curious reader, we recommend to visit the official web site of 3GPP, where all specifications can be downloaded for free.

3GPP Release 9 followed in 2009 and specifies some enhancements to the LTE System Architecture Evolution (SAE) and defines methods for interoperability between LTE and other access systems such as UMTS and WiMAX.

At the moment 3GPP is working on the 3GPP Release 10 known as LTE-advanced. LTE-advance is a preliminary standard that was formally submitted at ITU-T in the fall 2009, and expected to be finalized in 2011 with the target of meeting the IMT Advanced requirements for 4G as defined by ITU such as peak data rates up to 1 Gbps.

Table 3 summarizes the events occurred in the LTE standardization process and the actual work in progress. In order to understand correctly the content of the table, note that 3GPP standards are typically released in 3 stages:

  • Stage 1 refers to the standard description from a standards’ user point of view;
  • Stage 2 is a logical analysis, breaking the problem down into functional elements and the information flows amongst them;
  • Stage 3 is the concrete implementation of the protocols between physical elements onto which the functional elements have been mapped.

Table 3: events in LTE standardization process

The presence of many actors (stakeholders) in formal standardization makes it difficult to reach agreement in the process, resulting in longer time for the finalization of the standard than de facto standardization. Note, indeed, that the 3GPP Release 7 took more than two years to be completed. However, the situation is different in the case of the 3GPP Release 8 whose completion was achieved within one year. This can be attributed to the collaboration among various stakeholders and support organizations to test and validate the technology in a real-world setup and feeding the results of such tests back to 3GPP.

LTE Technology convergence phases

If the previous paragraph treated with the standardization stages accomplished by 3GPP in the LTE standardization process, this paragraph focuses on the roles that NGMN and LSTI alliances, and service providers have played in the overall developments towards LTE standardization. Three phases can be identified.

Phase 1 started in September 2006 with the NGMN alliance formation among major service providers to formulate their requirements for a 4G wireless communication system and set the stage for various vendors to standardize the same in LTE specification. The formation of the LSTI alliance and LTE Proof-of-Concept (PoC) trials occurred in this phase as well. Phase 1 ended with the stage 2 freeze of the LTE standard.

Phase 2 has seen LTE gaining more emphasis and importance between vendors at the expense of other competing technologies, and also it has seen major development in LTE technology. This phase started in July 2008 when NGMN approved LTE as it first compliant technology. That triggered Sprint, which was one of the founders of the alliance, to leave NGMN. This is partly due to Sprint’s decision to adopt WiMAX as choice of technology for their next generation network. In November 2008, Qualcomm halted the UMB project and shifted focus fully on to LTE technology. In January 2009, Nokia ended the production of its only WiMAX device. In October 2008, Bell and Telus declared a joint plan to move from CDMA to HSPA in 2010 and then to LTE in 2012. Regarding the alliances, LSTI members continued their focus on performing the technology trials and interoperability trials to refine the technology, while NGMN released its final requirements. Stage 3 freeze of the LTE standard was achieved in this phase.

Phase 3 (1Q 2009) started with commitments to adopt LTE by the biggest service providers which started to award the commercial contracts to deploy LTE to the vendors. In February 2009, Verizon announced their LTE deployment plans and selected various vendors for the network. The global mobile suppliers association announced that 26 major service providers have committed to deploy LTE systems.

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