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The LTE Standard Whitepaper - April 2014.pdf

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THE LTE STANDARD Developed by a global community to support paired and unpaired spectrum deployments April 2014 Prepared by Signals Research Group Project commissioned by Ericsson and Qualcomm Signals Research Group conducted a comprehensive review of the 3GPP standardization process and the underlying specifcations that defne LTE. Te analysis sought to identify and quantify the similarities and diferences within the overarching LTE specifcation documents as they pertain to the implementa
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  THE LTE STANDARD Developed by a global community to support paired and unpaired spectrum deployments April 2014 Prepared by Signals Research GroupProject commissioned by Ericsson and Qualcomm Signals Research Group conducted a comprehensive review of the 3GPP standardization process and the underlying specifications that define LE. Te analysis sought to identify and quantify the similarities and differences within the overarching LE specification documents as they pertain to the implementation require-ments for specific frequency bands, with a particular focus on paired (FDD) and unpaired (DD) spectrum. Tis whitepaper provides the findings from that study, including the results from our review of nearly 83,000 3GPP submissions, which demonstrate that the overwhelming majority of submissions occurring during a six-year period apply to both LE duplex schemes and that companies from all over the globe supported and contributed to the modest number of submissions which  were more specific to LE operating in paired or unpaired spectrum. As the sole authors of this paper, we stand fully behind the analyses and opinions that are presented in this paper. In addition to providing consulting services on  wireless-related topics, Signals Research Group is the publisher of the Signals Ahead   research newsletter. Te views and opinions expressed in this paper may not reflect the views and opinions of Ericsson and Qualcomm. www.signalsresearch.com  Page 2 April 2014 www.signalsresearch.com The LTE STANDARD Developed by a global community to support paired and unpaired spectrum deployments 1.0 Executive Summary Signals Research Group (SRG) conducted an exhaustive analysis of the 3GPP standardization process that led to the development of LE, and we reviewed all of the primary specifications that define the LE standard. Tere is a misconception among some of the industry followers that LE systems configured to operate in unpaired (LE DD) or paired (LE FDD) spec-trum have different srcins, different technical characteristics, and different prominent contribu-tors in the 3GPP standardization process.  Te objective of the whitepaper is to correct this misconception and establish that LE is one standard developed by organizations from all over the world. It is truly a global standard, having been designed to operate in both paired and unpaired spectrum bands with a minimum amount of additional complexity. In this whitepaper we use LE DD to refer to the unpaired mode of LE since this is the term used within the 3GPP standards body. However, D-LE is also commonly used instead of LE DD. A further objective is to identify and quantify the similarities and differences between LE as specified for use on paired spectrum, in which the downlink and uplink communications use different channels, and LE as specified for use in unpaired spectrum, in which the downlink and uplink communications share a common radio channel and divide time. Based on this study,  which included categorizing nearly 83,000 submissions that were submitted to the 3GPP over a six-year period (April 2005 through February 2011), we offer the following observations: The overwhelming majority of 3GPP submissions for LTE are duplex scheme agnostic, meaning that they apply equally to both duplexing options.  We identified 42,957 submissions out of 82,657 total that pertain to the development of the LE standard. Of these submission docu-ments, 82.5% of them do not distinguish in any way between the two duplex modes, meaning that only 17.5% of all LE submissions contain duplex-specific language. aking it one step further,  we classified only 7.0% of the documents as pertaining to LE DD and 3.7% of the documents as relating specifically to LE FDD. An additional 6.8% of the documents discuss both duplex schemes. We included all of these documents even though the language in the documents could merely state that the recommendation applies equally to both duplex schemes. A subjective review of these documents would have identified these occurrences and resulted in a lower percentage  versus our all-inclusive approach which inevitably includes “false positives” in the results. Net-Net:  Te actual number of submissions that identify duplex-specific features and recommendations accounts for as few as 10.7% and no more than 17.5% of all submissions pertaining to LE. LTE is one standard developed by organizations from all over the world. LTE Duplex Specific 17.5% LTE Duplex Neutral 82.5% LTE TDD Only 7.0% LTE FDD Only 3.7% LTE FDD & LTE TDD 6.8% 7,51035,447No. of LTE Submissions LTE Duplex NeutralLTE Duplex Specific Distribution of 3GPP Submissions by Duplex Scheme Source: Signals Research Group  Page 3 April 2014 www.signalsresearch.com The LTE STANDARD Developed by a global community to support paired and unpaired spectrum deployments  We identified at least 104 companies that submitted contributions to the 3GPP standardization process during the timeframe of the review. Of these companies, 58 companies made contribu-tions that specifically address LE DD and 52 companies made contributions that specifically address LE FDD. Further, no single country or region can claim it had more influence during the standardization process. Europe was the largest contributor with 28% of all LE DD submissions coming from the region. Other large contributors included the United States (23%), China (19%), South Korea (17%) and Japan (10%). Relative to the total number of contributions, each country’s/region’s contributions to LE DD was between 4.1% and 9.1% of its total LE contributions and for LE FDD the range was between 3.5% and 4.2%. There is a very high degree of commonality in the technical specifications (TS) between the FDD and TDD modes of LTE. Based on our review of eight S documents which define the majority of the LE radio access network (RAN) as well as other pertinent specifications and publications, it is very apparent that the overwhelming majority of the specifications are duplex agnostic, meaning that they apply equally to both duplex schemes. While perhaps self-evident to most industry followers, LE FDD and LE DD share a common core network with abso-lutely no distinction between the two duplexing modes of LE. LE FDD and LE DD are virtually identical with the exception of a few technical charac-teristics that are specific to the Physical Layer. Examples where the two LE modes are largely identical include the downlink physical layer channels, the use of resource blocks, the mapping of control channels to resource elements, the channel coding, the scrambling of each code word, the modulation types and how they work, and the basic implementations of MIMO. In the uplink, areas with large commonalities include the use of SC-FDMA, control channels (PUCCH), modulation schemes, channel coding, how resource elements are mapped in the frequency and time domain, and PRACH (Physical Random Access Channel), which defines the Physical Layer channel that carries attempts by the mobile device to access the system, including responses to LTE FDD and LTE TDD are virtually identical with the exception of a few technical characteristics that are specific to the Physical Layer. Source: Signals Research Group Other 3% China 19% South Korea 17%  Japan 10% US 23% Europe 28% Other 6% China 13% South Korea 15%  Japan 17% US 19% Europe 30% LTE TDD LTE FDD LTE Duplex Neutral Other 5% China 12% South Korea 15%  Japan 16% US 22% Europe 30% Country/Regional Distribution of Submissions to the 3GPP RAN Working Groups  Page 4 April 2014 www.signalsresearch.com The LTE STANDARD Developed by a global community to support paired and unpaired spectrum deployments paging messages and requests to transmit data. For both duplex schemes, the Medium Access Control (MAC) Layer is identical, with one minor distinction, the RLC (Radio Link Control) Layer is identical, and the Radio Resource Control (RRC) Layer is essentially identical, with some distinction regarding when a couple of messages can be sent. Tere are some differences between the LE FDD and LE DD modes that we identified, but these differences primarily pertain to when an action or event is done and not to why or how something is executed. Te differences associated with when something is done stem from the discontinuous downlink/uplink transmissions that are an inherent part of any DD duplex scheme. In a similar fashion there are also differences, or what are perhaps better classified as options/configurations, within each duplex scheme. Tese unique configurations allow LE to be deployed in 34 different frequency bands – 23 LE FDD and 11 LE DD – support six potential channel bandwidths, and seven possible downlink/uplink configurations for LE DD. A global contingent of operators and vendors harmonized LTE TDD on a single frame struc-ture, even though it removed some commonality with earlier time-division-duplexing-based 3GPP 3G standards.  During the early development stages of LE, LE DD had two frame structure options, including one frame structure that was very similar to the frame structure used by D-SCDMA (or LCR DD, as it is referred to in the 3GPP specifications). Other than this distinction, LE DD had little, if anything, in common with earlier time-division-duplexing-based 3GPP 3G standards. Following the initial recommendations by China Mobile, Vodafone Group, and Verizon Wireless, the 3GPP RAN Working Group agreed to “a single optimized DD mode, based on Frame Structure 2, further optimizing performance and ensuring ease of imple-mentation of FDD and DD modes within the same E-URA equipment.” Following this decision within 3GPP the LE specifications no longer support a relationship that previously existed with LCR DD. Further, this action was consistent with an earlier recommendation from Vodafone Group, -Mobile International, eliaSonera, and elefonica that: “Unnecessary fragmentation of technologies for paired and unpaired band operation shall be avoided. Tis shall be achieved with minimal complexity.”   Operators recognized that the pitfalls associated with the large discontinuity between how the 3G (UMS) specifications defined FDD and DD modes resulted in the unsuccessful market adoption of a global 3G solution for their unpaired spectrum.  A recent IEEE paper 1  from engineers at Datang elecom further reinforces this approach.  Te papers states, “…during the process of developing LE and LE-Advanced specifications, the maximum commonality between DD and FDD has been emphasized in the Tird Generation Part-nership Project (3GPP), and realized by achieving a good balance between the commonality of basic structures and optimization of individual characteristics.”  1 Technical Innovations Promoting Standard Evolution: From TD-SCDMA to TD-LTE and Beyond, Shanzhi Chen, Yingmin Wang, Weiguo Ma, and Jun Chen, State Laboratory of Wireless Mobile Communications, China Academy of Telecommunications Technology, IEEE Wireless Communications, February 2012 Differences between the FDD and TDD modes primarily pertain to when an action or event is done and not to why or how something is executed.
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