Agilent Measurement Journal - Issue 4 - 2008 - (Page 19)

C Close on the heels of IEEE’s new 802.16e standard—better known as Mobile WiMAX TM — follows the response from the Third-Generation Partnership Project (3GPP) in the form of its Long-Term Evolution (LTE) project. We featured WiMAX TM in Issue Three of Agilent Measurement Journal and in this article we explore what LTE aims to bring to the wireless ecosystem. After considering the broader aspects of LTE, we take a closer look at the uplink, which uses a new modulation format called single-carrier frequency-division multiple access (SC-FDMA). These are interesting times because it is rare that the communications industry rolls out a new modulation format. From both a technical and practical point of view, there is much to understand, examine and evaluate in the capabilities and beneﬁts that SC-FDMA brings to LTE. SC-FDMA is a hybrid modulation scheme that combines the low peak-to-average ratio (PAR) of traditional single-carrier formats such as GSM with the multipath resistance and in-channel frequency scheduling ﬂexibility of orthogonal frequency-division multiplexing (OFDM). This does not mean the end of 3GPP’s interest in GSM and W-CDMA. Rather, the investment in these technologies — and their remaining untapped potential — means that LTE is not the only format being developed in 3GPP Release 8. For example, the EDGE Evolution project will be pushing GSM to newer levels and the HSPA+ project — the runner-up to OFDM for LTE — will continue to evolve the underlying W-CDMA, HSDPA and HSUPA technologies. For an overview of how these formats inter-relate, please see “What Next for Mobile Telephony?” in Issue Three of Agilent Measurement Journal. By using OFDM, LTE is aligning with similar decisions made by 3GPP2 for Ultra-Mobile Broadband (UMB) and by IEEE 802.16 for WiMAX. For an overview of OFDM technology, please see “Understanding the Use of OFDM in IEEE 802.16 (WiMAX)” in Issue Two of Agilent Measurement Journal. Although the article explains the basics of OFDM with reference to WiMAX, the general principles apply to LTE and UMB as well. Within the formal 3GPP speciﬁcations, the LTE evolved RAN is split into two parts: the Evolved UMTS Terrestrial Radio Access (E-UTRA) describing the mobile part; and the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) for the base station. For simplicity, this article refers to the new air interface by its project name, LTE. This is becoming common usage just as happened with another project name, UMTS, which has been synonymous with W-CDMA since 1999. In addition to developing LTE, 3GPP is also working on a complementary project known as System Architecture Evolution (SAE), which deﬁnes the split between LTE and a new Evolved Packet Core (EPC), which is a ﬂatter packet-only core network that aims to deliver the higher throughput, lower cost and lower latency promised by LTE. The EPC is also designed to provide seamless interworking with existing 3GPP and non-3GPP access technologies. Acronyms galore: LTE history and context LTE’s study phase began in late 2004. The overall goal was to select technology that would keep 3GPP’s Universal Mobile Telecommunications System (UMTS) at the forefront of mobile wireless well into the next decade. Key project objectives were set in the following areas: peak data throughput; spectral efﬁciency; ﬂexible channel bandwidths; latency; device complexity; and overall system cost. The main decision was whether to pursue the objectives by continuing to evolve the existing W-CDMA air interface (which incorporates HSPA*) or adopt a new air interface based on OFDM. At the conclusion of the study phase, 3GPP decided that the project objectives could not be entirely met by evolving HSPA. As a result, the LTE evolved radio access network (RAN) is based on a completely new OFDM air interface. *HSPA (high-speed packet access) refers collectively to high-speed downlink packet access (HSDPA) and high-speed uplink packet access (HSUPA), the latter being formally known as the Enhanced Dedicated Channel (E-DCH). Agilent Measurement Journal 19

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 4 - 2008

Agilent Measurement Journal - Issue 4 - 2008 Delivering Confidence through Compliance with Standards Contents Emerging Innovations Trying Early Device Implementations at the IEEE 1588 PlugFest Achieving Greater Confidence in Measurement Accuracy through Consistency in Calibration Services Overcoming the Challenges of RFID Component Testing 3GPP LTE: Introducing Single- Carrier FDMA Ensuring Reliable Operation and Performance in Converged IP Networks Testing Storage Area Networks and Devices at 8.5-Gb/s Fibre Channel Rates Choosing an Appropriate Calibration Method for Vector Network Analysis Making Traceable EVM Measurements with Digital Oscilloscopes Exploring Terahertz Measurement, Imaging and Spectroscopy: The Electromagnetic Spectrum’s Final Frontier Interpreting Quoted Specifications when Selecting Digitizers

Agilent Measurement Journal - Issue 4 - 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.