WHAT IS 4G? A Closer Look at WiMAX and LTE
WHAT IS 4G? A Closer Look at WiMAX and LTE A BRIEF HISTORY OF MOBILE COMMUNICATIONS 2G – 2nd generation of mobile telephony technology; launched in 1991. Main benefits of 2G: phone conversations were digitally encrypted; 2G is significantly more efficient on the spectrum allowing for greater mobile phone penetration levels; 2G introduced data services for mobiles, starting with SMS text messages. 2G technologies can be divided into TDMA-based and CDMAbased standards depending on the type of multiplexing used. The main 2G standards are GSM, IS-95 (CDMA), iDEN, PDC (personal digital cellular), IS-136 (aka D-AMPS digitaladvanced mobile phone service which is TDMA). HISTORY OF TELECOMMUNICATIONS 2.5/2.75 G –are 2G-systems that have implemented a packet-switched domain in addition to the circuit-switched domain. The first major step in the evolution of GSM networks to 3G occurred with the introduction of General Packet Radio Service (GPRS), and EDGE Enhanced Data for GSM Evolution which is sometimes referred to as EGPRS. CDMA2000 networks similarly evolved through the introduction of 1XRTT. EDGE is standardized by 3GPP as part of the GSM family and it is an upgrade that provides a potential three-fold increase in capacity of GSM/GPRS networks. The specification achieves higher data-rates (up to 236.8 kbit/s) by switching to more sophisticated methods of coding (8PSK), within existing GSM timeslots. A BRIEF HISTORY OF MOBILE COMMUNICATIONS 3G – third generation of mobile telephone technology. 3G refers to the generation of standards as described by (International Mobile Telecommunications) IMT-2000 by the International Telecommunications Union (ITU). Apps include wide area voice telephone, mobile internet access, video calls and mobile TV all in a mobile environment. The IMT-2000 standards requires a system to provide peak data rates of at least 200 kBps. The main 3G standards are UMTS (Universal Mobile Telecommunications System) which is the 3G upgrade to the GSM networks and CDMA2000, the 3G upgrade to the CDMA networks. UMTS standards are put forth by the 3GPP (Third Generation Partnership Project); CDMA2000 standards are put forth by 3GPP2, the standardization group of CDMA2000. 3GPP is a collaboration between groups of telecommunications associations, known as the Organizational Partners. A BRIEF HISTORY OF MOBILE COMMUNICATIONS GSM/GPRS/EDGE/W-CDMA is the most widespread wireless standard in the world. A few countries (such as the USA, India, South Korea and Japan) use both sets of standards, but most countries use only the GSM family. A BRIEF HISTORY OF MOBILE COMMUNICATIONS 4G Not quite yet! 3.5, 3.75G OR 3.9G (transitional)– 3GPP2 family – CDMA2000 1XEV-DO Rev A,B. 3GPP family – HSPA, HSPA+, LTE(E-UTRA). IEEE family – 802.16e-2005 (mobileWiMAX). A BRIEF HISTORY OF MOBILE COMMUNICATIONS CDMA2000 1xEV-DO (Evolution Data Only or Optimized) Rev A – Enhancement to 1X EV-DO Rev. 0. EVDO is standardized by (3GPP2) as part of the CDMA2000 family of standards. EV-DO was designed as an evolution of the CDMA2000 standard that would support high data rates and could be deployed alongside a wireless carrier's voice services. An EVDO channel is 1.25Mhz wide. CDMA 2000 Rev A - can support 3.1MBps in the DL and 1.8MBps in the UL. CDMA 2000 Rev B – released in 2010. Can support 4.9X(N) MBps in the DL and 1.8X(N) MBps in the UL. A BRIEF HISTORY OF MOBILE COMMUNICATIONS HSPA – High Speed Packet Access is an combination of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUDA), These protocols improve the performance of existing WCDMA protocols. HSPA supports increased peak data rates of up to 14 Mbit/s in the downlink and 5.8 Mbit/s in the uplink. It also reduces latency and provides up to five times more system capacity in the downlink and up to twice as much system capacity in the uplink. HSPA+ - A wireless broadband standard defined in 3GPP release 7 and 8 of the WCDMA specification. Evolved HSPA provides data rates up to 84 Mbit/s in the downlink and 22 Mbit/s in the uplink (per 5 MHz carrier) with multiple input, multiple output (MIMO) technologies and higher order modulation. 4G Why do we need 4G? Did you know there are more mobile phones on the planet than… Automobiles PCs TVs COMBINED!!! Data rates are expected to climb dramatically as more data-extreme apps are available. The mobile industry technology is the most rapidly adopted technology in the world. 4G 4G is the fourth-generation of mobile telecommunication technology standards as set by the ITU-R (radio sector), the standards are the IMT-Advanced set of standards. IMT-Advanced specifies a 4G network must achieve 1GBps DL speeds while stationary and 100MBps while mobile. Based on an all-IP packet switched network. Peak data rates of up to approximately 100 Mbit/s for high mobility such as travel on trains or cars, and up to approximately 1 Gbit/s for low mobility such as nomadic/local wireless access, according to the ITU requirements. Dynamically share and use the network resources to support more simultaneous users per cell. 4G Scalable channel bandwidth 5–20 MHz, optionally up to 40 MHz. Peak link spectral efficiency of 15 bit/s/Hz in the downlink, and 6.75 bit/s/Hz in the uplink (meaning that 1 Gbit/s in the downlink should be possible over less than 67 MHz bandwidth). System spectral efficiency of up to 3 bit/s/Hz/cell in the downlink and 2.25 bit/s/Hz/cell for indoor usage. Smooth handovers across heterogeneous networks. Ability to offer high quality of service for next generation multimedia support. 4G Both LTE Advanced and 802.16m (WirelessMAN Advanced evolution of 802.16e) are considered 4G. 4G is expected to provide a comprehensive and secure all-IP based mobile broadband solution to laptop computers, wireless modems, smartphones, and other mobile devices. 4G OR FAUX G?? Are these speeds available now??? Where can I sign up??? Unfortunately, no. LTE Advanced and 802.16m (WirelessMAN Advanced) are still under development and are the only two technologies designated by the ITU to fulfill the IMT-Advanced requirements. They are expected to be finalized in 2011. What is available now isn’t Faux G, it is 4G as the ITU announced that current versions of LTE, WiMax and other evolved 3G technologies that do not fulfill "IMT-Advanced" requirements could be considered "4G", provided they represent forerunners to IMT-Advanced and "a substantial level of improvement in performance and capabilities with respect to the initial third generation systems now deployed." WE’LL COVER… IEEE 802.16 WiMAX and LTE Network architecture Multiplexing technique Subcarriers Physical channel Modulation and coding MIMO WHAT IS 802.16? IEEE is known for defining LAN standards and supporting technologies. Over the last few decades, IEEE 802 group has defined a number of widely successful LAN technologies. These included Ethernet and Wireless LAN (a.k.a. Wi-FI). 802.16 is a broadband wireless alternative to wireline last mile (such as DSL, cable modems, and T1s. The 802.16 subcommittee has been tasked with defining Broadband Wireless Access (BWA) technology. The mandate includes defining BWA for fixed, portable and mobile applications. 802.16 802.16 has defined both Point-to-Point (PTP) and Point to Multipoint (PMP) systems. PMP systems offer both fixed and mobile. These access technologies are designed as an alternative to wireline broadband technologies such as DSL, cable modems and T1s. IEEE 802 LAN/MAN STANDARDS COMMITTEE 802.3 – Ethernet 802.11 – WLAN 802.15 – WPAN (Wireless Personal Area Network) 802.16 – Fixed, Portable & Mobile BWA 802.20 – Mobile BWA - an IEEE standard to enable worldwide deployment of multi-vendor interoperable mobile broadband wireless access networks. 802.21 – MIH Media Independent Handover – handover and interoperability between both 802.X and non 802.x networks. 802.16 KEY FEATURES It is designed to work in both licensed and unlicensed spectrums and defines features to mitigate interference in the unlicensed spectrum. It can support different channel bandwidths to accommodate different spectrum allocations in different countries. It supports both Time Division Duplex (TDD) and Frequency Division Duplex (FDD) modes. The channel bandwidth may range from 1.25MHz to 20MHz.; i.e. 5/10/20MHz, 3.5/7/14MHz It operates in the 2.3-GHz, 2.5-GHz, 3.5-GHz, and 5.8-GHz frequency bands. TDD appears to be the most popular with operators primarily due to cost and availability of spectrum. Speed: Mobile Wimax technology (802.16e)supports DL data rates up to 63MBps per sector and UL data rates up to 28MBps in a 10MHz channel and 128MBps DL and 56MBps UL in a 20MHz. These speeds are achieved by the flexible sub-channelization schemes, adaptive modulation and coding and MIMO antenna techniques. 802.16 A/D (802.16-2004) IEEE 802.16 defines a series of link layer technologies for wireless MAN applications. The standard series is known as 802.16 a/d and defines 5 flavors of access technology, they are: WirelessMAN – Single Carrier – suitable for PTP and PMP access. WirelessMAN – Single Carrier Access – Typically used for PTP. WirelessMAN – OFDM256 – defines fixed PMP operation and uses licensed bands under 11GHz. WirelessMAN – OFDMA2048- defines fixed PMP operation as well and uses licensed bands under 11GHz. WirelessHUMAN – defined for operation in an unlicensed spectrum and which could use any of the air interfaces SCa, OFDM, and Orthogonal Frequency Division Mutliplexing Access (OFDMA). 802.16E – MOBILE WIMAX The 802.16e amendment adds the mobility component to the 802.16 standard. The 802.16e air interface is based on Scalable OFDMA (SOFDMA), which is designed to support mobility. 802.16 The 802.16 standard defines Physical (PHY: layer 1) and Medium Access Control (MAC; layer 2) layers of the OSI (Open Systems Interconnection) model. OSI model: The OSI model is a 7 layer model created to standardize the rules of networking in order for all systems to be able to communicate. In order for communication to occur on a network using different device drivers and protocol stacks, the rules for communication must be explicitly defined. The OSI model deals with the following issues; How a device on a network sends its data, and how it knows when and where to send it How a device on a network receives its data, and how to know where to look for it. How devices using different languages communicate with each other. How devices on a network are physically connected to each other. How protocols work with devices on a network to arrange data. 802.16 OSI model 7 layers are: 1. Physical Layer 2. Data Link Layer 3. Network Layer 4. Transport Layer 5. Session Layer 6. Presentation Layer 7. Application Layer 802.16 Physical layer – this layer is responsible for transmission and reception of OFDM symbols, power control, modulation and coding. MAC layer (consists of 3 parts)– this layer is responsible for: Connection establishment between the subscriber station and network. It defines messaging for authentication, IP address allocation and dynamic addition/deletion of services. Scheduling bandwidth for different users; it performs bandwidth allocation based on user requirements as well as their Quality of Service (QoS) profiles. Performing initial system acquisition when the mobile powers up, and performs timing synchronization with the network through ranging procedures. In 802.16e, this layer also handles radio mobility procedures to provide full mobility for the mobiles. 802.16 MAC layer continued: Responsible for mapping Asynchronous Transfer Mode (ATM) and IP packets to MAC layer Protocol Data Units (PDU), which are then mapped on top of PHY layer radio channels. Defines authentication procedures to mutually authenticate the subscriber and the network. Defines encryption mechanisms to encrypt user traffic and control messages. Defines a key management technique to dynamically update authentication and encryption keys to enhance the security of the system . SO WHAT IS WIMAX? WiMAX is Worldwide Interoperability for Microwave Access It is the name of the trade association formed by a group of network manufacturers, operators and service integrators that promotes the broadband wireless technology defined by the 802.16 committee. The WiMAX forum is to Wimax as the Wi-Fi Alliance is to 802.11. WIMAX FORUM 802.16 defines the BWA radio interface technology but doesn’t define the end-to-end network architecture. WiMAX Forum performed that task; they defined a standards-based end-to-end network architecture which is essential for successful interoperability among network elements from various vendors and among networks of various operators. This network architecture defined by the WiMAX Forum is an All-IP-based architecture. WIMAX FORUM WiMAX Forum also acts as the certification and verification body for vendor equipment. The Forum must ensure the manufacturers implement a certain set of features defined by 802.16 standards. To do this, the Forum defines system profiles that define all of the features that must be supported by the equipment manufacturers. The WiMAX Forum also provides technical leadership. WIMAX 802.16 defines layer 1 and layer 2 only. It also defines radio mobility aspects that enable Mobile Stations (MS) to change a radio link from one transmitter to the another transmitter and it defines system profiles that detail lists of mandatory and optional features required in the radio interface. WiMAX Forum defines a standardized network architecture beyond the air link aspect of the base station and defines mobility across different networks. WIMAX NETWORK Between the MS and internet, the WiMAX Network Architecture is basically defined as two networks: The Access Services Network (ASN) The Connectivity Services Network (CSN) WIMAX NETWORK ASN – includes the base station (BS) and an ASNGateway (ASN-GW). The BS controls radio access, handover control and resource scheduling. The ASN-GW provides functions in support of managing and maintaining data paths for services, and performs the role of a context server and paging controller for MSs that are in “idle”mode. The ASN-GW is connected to a number of BSs. The ASN-GW performs roles similar to the BSC in 2G networks and RNC in 3G networks. WIMAX NETWORK CSN – this includes a Domain Name Server (DNS), an authentication, authorization and accounting server (AAA), a mobile IP Home Agent (HA), which provides allocation of dynamic IP address and a Dynamic Host Configuration Protocol (DHCP) server. The DHCP provides address configuration. The CSN provides most of the backend functions such as authentication, IP address management, billing and mobility to the ASN and tunneling support. The HA works with a Foreign Agent (FA) at the ASN-GW and is responsible for forwarding user traffic to the FA serving the MS. The FA is router serving as a mobility agent for an MS. WIMAX NETWORK A single ASN may connect to the multiple CSNs and vice versa. The ASN and CSN can be owned by different business entities. The ASN provider is known as the Network Access Provider (NAP) and the CSN is known as a Network Service Provider (NSP). WIMAX NETWORK Figure 1. WiMAX Network (Award Solutions, Exploring WiMAX, 2009) QOS MODEL 802.16 is designed to support a wide range of applications that require different levels of Quality of Service (QoS). To accommodate these apps, the 802.16 standard has defined five service classes. WiMAX is QoS driven. UGS – Unsolicited Grant Service RT-VR – Real Time-Variable Rate Needs guaranteed QoS, minimum delay and jitter. Commercial IP/TV, T1. Guaranteed average data rate, can tolerate small variable delays between packets. Steaming Music. ERT-VR – Extended Real Time-Variable Rate Variable Rate with minimum delay between packets. VOIP with silence suppression. QOS MODEL NRT-VR – Non-Real-Time Variable Rate Variable rate, can tolerate longer delay between packets. FTP, Web browsing. BE – Best Effort Just that, best effort. Non-real-time apps with very low delay sensitivity. Email retrieval. OFDM WiMAX air interface is based on OFDM/OFDMA. OFDM uses multiple sub-carriers, the sub-carriers are closely spaced to each other without causing interference, this allows the removal of guard bands between adjacent sub-carriers. This is possible because the frequencies (sub-carriers) are orthogonal, meaning the peak of one subcarrier coincides with the null of an adjacent sub-carrier. In an OFDM system, a very high rate data stream is divided into multiple parallel low rate data streams. Each smaller data stream is then mapped to individual data sub-carrier and modulated using some sorts of PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation). i.e. BPSK, QPSK, 16-QAM, 64-QAM. OFDM needs less bandwidth than FDM to carry the same amount of information which translates to higher spectral efficiency and it is more resilient in a NLOS environment. OFDM can efficiently overcome interference and frequency-selective fading caused by multipath because equalizing is done on a subset of sub-carriers instead of a single broader carrier. The effect of ISI (Inter Symbol Interference) is suppressed by virtue of a longer symbol period of the parallel OFDM sub-carriers than a single carrier system and the use of a cyclic prefix (CP). OFDMA Whereas OFDM is a modulation technique, OFDMA is a multiple access technique used primarily in mobileWiMAX and allows different users to have access to the available channel at the same time. OFDMA is a multi-user version of the OFDM digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users In an OFDM based system, entire subcarriers are allocated to only one user, while in OFDMA subcarriers are divided into different groups of subcarriers and each group has a number of subcarriers, known as sub-channels. OFDMA OFDM-TDMA OFDMA includes OFDM-TDMA as one of the possible modes of operation. Users are allocated capacity only on the basis of time. Each user is given a time slice periodically; the time slices are allocated in terms of number of OFDM symbols. i.e. If each time slice is two OFDM symbols, a user is allocated all the subcarriers for two OFDM symbols. No granularity in the frequency domain is provided because all subcarriers are allocated to the same server. OFDMA In OFDMA allocation is possible in both time and frequency dimensions. In theory, every intersection of symbol time and subcarrier frequency is uniquely assignable. This allows any given frame to support many simultaneous subscribers and their respective sessions. OFDMA The two primary variables in an OFDM system are the symbol time and the subcarrier spacing. Symbol time and subcarrier spacing are related by the following: Subcarrier spacing=1/T, T is the Symbol Time The subcarrier spacing is fixed, this allows the bandwidth scalability. SCALABLE OFDMA (SOFDMA) SOFDMA is the scalable form of the OFDMA, which is employed by mobileWiMAXnetworks. In this scheme, the number of the subcarriers which is equal to the size of FFT, scales with the bandwidth, while maintaining each sub-channel’s bandwidth constant; which means the subcarrier spacing and the number of the subcarriers are independent of the bandwidth. SCALABLE OFDMA (SOFDMA) For a given channel bandwidth, the subcarrier spacing is inversely proportional to the number of subcarriers and, therefore, the FFT size. The time duration of the OFDMA symbol is set by the inverse of the subcarrier spacing. Therefore by fixing the subcarrier spacing, the symbol time is automatically specified. The inverse relationship between subcarrier spacing and symbol duration is a necessary and sufficient condition to ensure that the subcarriers are orthogonal. By fixing the subcarrier spacing and symbol time, this ensures channel/hardware conditions are the same at vary bandwidths. SOFDMA Figure 2 – Subcarrier spacing SOFDMA Same subcarrier spacing is maintained for different channel bandwidths. OFDMA symbol duration and cyclic prefix is the same, resulting in the same effects due to multipath. With the subcarrier spacing the same, this then implies the same sensitivity to frequency offset, phase noise and Doppler Shift (the effects due to the various channel/hardware conditions are the same at varying bandwidths). SCALABLE OFDMA PARAMETERS For frequencies, 1.25, 5, 10 and 20MHz, these are the parameter values: Subcarrier frequency spacing (Delta f)= 10.9375kHz Useful symbol time (Tb=1/Delta f) = 91.43us Guard time or cyclic prefix (Tg=Tb/8) = 11.43us Could be ¼, 1/8, 1/16 and 1/32 and is chosen based on certain assumptions about the wireless channel. Total OFDM symbol time (Ts=Tb+Tg) = 102.86us SCALABLE OFDMA – FRAMES & SUBCHANNELS Symbols and subcarriers are organized into frames. The OFDMA frame consists of a DL sub-frame and an UL sub-frame. The flexible frame structure of the TDD signal consists of a movable boundary between the DL and UL sub-frames. Each TDD frame includes a DL subframe, followed by a Transmit/Receive Transition Gap (TTG), followed by the uplink subframe, finally followed by a Receive/Transmit Transition Gap (RTG). In MobileWiMAX 47 total symbols are used in the DL and UL subframes for 5 and 10MHz channels. The remaining time is used for the TTG and RTG. Recall a total OFDMA symbol is 103us. This DL subframe begins with a Preamble which is one symbol time and is used for BS identification, timing synchronization, and channel estimation at the MS. The preamble consists of a Pseudo Number (PN) sequence used to acquire and synchronize with the system. The data in the preamble is mapped to every third subcarrier, using BPSK, giving a modest peak-to-average power level compared to the data subchannels. OFDM-TDD PHY LAYER FRAME Figure 3 TDD PHY Layer Frame (Award Solutions, Exploring WiMAX, 2009) SCALABLE OFDMA – FRAMES & SUBCHANNELS WiMAX groups symbols into frames and subcarriers into subchannels. A user is allocated one or more subchannels for all or part of a frame. Subchannel allocation schemes: PUSC, FUSC and Band AMC (Adaptive Modulation and Coding) are schemes for assigning subcarriers to subchannels. There are more, these are the most often used. Modulation: There are three modulation types available for modulating the data onto the subcarriers: QPSK, 16QAM, and 64QAM. Binary phase shift keying (BPSK) modulation is used during the preamble, on the pilots, and when modulating subcarriers in the ranging channel. In the UL, the transmit power is automatically adjusted when the modulation coding sequence (MCS) changes to maintain the required nominal carrier-to-noise ratio at the BS receiver. 64QAM is not mandatory for the UL. ADAPTIVE MODULATION & CODING Adaptive Modulation refers to the selection of different modulation and coding schemes by the transmitter and allows for the scheme to change on a burst-by-burst basis per link, based on the state of the channel. A transmitter has to transmit the data in as high as possible data rate if the channel has a good condition. However, if the condition of the channel is weak, the data rate must be as low as possible. The condition of the channel is mostly determined through the (Signal to Interference Noise Ratio) SINR measurement. Channel Coding: There are various combinations of modulations and code rates available in the OFDMA burst. Channel coding is the randomization of data, forward error correction (FEC) encoding, interleaving, and modulation. In some cases, transmitted data may also be repeated on an adjacent subcarrier. SCALABLE OFDMA – FRAMES & SUBCHANNELS Differences between the DL and UL signal: In the UL there isn’t a preamble, but there are an increased number of pilots. Pilots are the control and synchronization signal. Pilots in the UL are never transmitted without data subcarriers. UL uses special CDMA ranging bursts during the network entry process. Data is transmitted in bursts that are as long as the uplink sub-frame zone allows, and wrapped to further subchannels as required. WIMAX SUMMARY All IP network, heavily QoS driven, uses smart antenna technology to increase data speeds. Network architecture consists of ASN and CSN. ASN is BS and ASN-GW. CSN is typical of a ISPs backend network. SOFDMA Uses SOFDMA on radio access link. Subcarrier spacing is fixed. Subchannel allocation schemes are: PUSC, FUSC, Adaptive Modulation and Coding. SMART ANTENNA TECHNOLOGY Multiple antenna techniques: TX/RX Diversity Frequency Diversity. Delay diversity. STC Space Time Coding. MIMO Spatial Multiplexing (True MIMO). Beamforming Switched Beam Systems. Adaptive Beamforming. SDMA Space Division Multiple Access. MIMO MIMO: MIMO is the use of multiple antennas at both the transmitter and receiver to improve communication performance. offers significant increases in data throughput and link range without additional bandwidth or transmit power. It achieves this by higher spectral efficiency (more bits per second per hertz of bandwidth) and link reliability or diversity (reduced fading). This method transmits one data bit from the first antenna, and another bit from the second antenna simultaneously, per symbol. As long as the receiver has more than one antenna and the signal is of sufficient quality, the receiver can separate the signals. This method involves added complexity and expense at both the transmitter and receiver. However, with two transmit antennas and two receive antennas, data can be transmitted twice as fast as compared to systems using Space Time Codes with only one receive antenna. LTE 3GPP Long Term Evolution (LTE), is the latest standard in the mobile network technology tree that produced the GSM/EDGE and UMTS/HSPA network technologies. It is a project of the (3GPP), operating under a name trademarked by one of the associations within the partnership, the European Telecommunications Standards Institute. LTE may also be referred more formally as Evolved UMTS Terrestrial Radio Access (EUTRA) and Evolved UMTS Terrestrial Radio Access Network (E-UTRAN). e-UTRA or eUTRAN is the air interface of 3GPP’s LTE upgrade path for mobile networks. E-UTRAN is a radio access network standard meant to be a replacement of the UMTS, HSDPA and HSUPA technologies specified in 3GPP releases 5 and beyond. Unlike HSPA, LTE's E-UTRA is an entirely new air interface system, unrelated to and incompatible with W-CDMA. It provides higher data rates, lower latency and is optimized for packet data. It uses OFDMA radio-access for the downlink and SCFDMA on the uplink. LTE EUTRAN has the following features: Peak download rates of 292 Mbit/s for 4x4 antennas, 143 Mbit/s for 2x2 antennas with 20 MHz of spectrum. Peak upload rates of 71 Mbit/s for every 20 MHz of spectrum. Low data transfer latencies (sub-5ms latency for small IP packets in optimal conditions), lower latencies for handover and connection setup time. Support for terminals moving at up to 350 km/h or 500 km/h depending on the frequency band. Support for both FDD and TDD duplexes as well as half-duplex FDD with the same radio access technology. Market preferences dictate that the majority of deployed systems will be FDD. Support for all frequency bands currently used by IMT systems by ITU-R. LTE EUTRAN features: Flexible bandwidth: 1.4 MHz, 3 MHz, 5 MHz 15 MHz and 20 MHz are standardized. By comparison, W-CDMA uses fixed size 5 MHz chunks of spectrum. Increased spectral efficiency at 2-5 times more than in 3GPP release 6 (HSPA). Support of cell sizes from tens of meters of radius (femto and picocells) up to over 100 km radius macrocells. Simplified architecture: The network side of EUTRAN is composed only by the eNodeBs. Support for inter-operation with other systems (e.g. GSM/EDGE, UMTS, CDMA2000, WiMAX.) Packet switched radio interface. LTE NETWORK ARCHITECTURE LTE has only one network element, the eNB (evolved Node B). The eNB is similar to a base station in 2G/3G systems. eNBs support all Layer 1 and Layer 2 features associated to the E-UTRAN OFDM physical interface, and they are directly connected to network routers. The 3G RNC (Radio Network Controller) inherited from the 2G BSC (Base Station Controller) has disappeared from E-UTRAN and the eNB is directly connected to the Core Network using the S1 interface. The features supported by the RNC have been distributed between the eNB, the Core Network MME and the Serving Gateway entities. LTE NETWORK ARCHITECTURE Figure 4 – LTE Network Architecture LTE NETWORK ARCHITECTURE eNB – Evolved Node B – WLAN access point. eNB performs the following tasks: Radio bearer control. Radio admission control. Connection mobility management. Dynamic resource allocation. Inter cell interference coordination. Load balancing. The eNB is connected to the EPC by SI interface, and connected to other eNBs by X2 interface, this minimizes packet loss. LTE NETWORK ARCHITECTURE EPC (Evolved Packet Core) – consists of the following entities: MME – Mobility Management Entity This is the key control node for the LTE access network. Security procedures - end-user authentication Terminal-to-network session handling - signaling procedures used to set up Packet Data context and negotiate associated parameters like the Quality of Service. Idle-terminal location management - this relates to the tracking area update process. (idle) S-GW – Serving-GateWay Serves as a local mobility anchor. Packets are routed through this point for intra E-UTRAN mobility and mobility with other 3GPP technologies. LTE NETWORK ARCHITECTURE PDN-GW – Packet Data Network- GateWay This is the termination point of the packet data interface towards the Packet Data Network. It provides connectivity to the subscriber to external packet data networks by being the point of exit and entry of traffic for the subscriber. PCRF – Policy and Charging Rules Function Server This server manages the service policy and sends QoS setting information for each user session and accounting rule information. It also combines functionalities for the two UMTS nodes: The Policy Decision Function (PDF) and the Charging Rules Function (CRF). HSS – Home Subscriber Server This is a concatenation of the HLR (Home Location Register) and AuC (Authentication Center). LTE – PHYSICAL LAYER E-UTRA uses OFDM and MIMO antenna technology depending on the terminal category for the downlink and for the UL it uses both OFDM and Single Carrier FDMA (SC-FDMA) depending on the physical channel. LTE Frames: The generic radio frame for FDD and TDD has a duration of 10ms and consists of 20 slots with a slot duration of 0.5ms. Two adjacent slots form one sub-frame of length 1ms. A resource block spans either 12 sub-carriers with a sub-carrier bandwidth of 15kHz or 24 sub-carriers with a sub-carrier bandwidth of 7.5kHz each over a slot duration of 0.5ms. With the subcarrier spacing at 15 kHz apart from each other, to maintain orthogonality, this gives a symbol rate of 1 / 15 kHz = of 66.7 µs. LTE – PHYSICAL LAYER In the UL LTE uses both OFDMA and Single Carrier Frequency Division Multiple Access (SC-FDMA) depending on the channel. This is to compensate for a drawback with normal OFDM, which has a very high peak to average power ratio (PAPR). High PAPR requires more expensive and inefficient power amplifiers with high requirements on linearity, which increases the cost of the terminal and drains the battery faster. The modulation schemes supported in the downlink are QPSK, 16QAM and 64QAM, and in the uplink QPSK, 16QAM and 64QAM. The Broadcast channel uses only QPSK. The modulation scheme is dependent on the channel condition, mainly SINR. Coding: The channel coding scheme for transport blocks in LTE is Turbo Coding with a coding rate of R=1/3, two 8-state constituent encoders and a contention-free quadratic permutation polynomial (QPP) turbo code internal interleaver. WIMAX VS. LTE Similarities: They have similar network architecture. All-IP network. The two standards both define layer 1 and layer 2 of the OSI model. use OFDMA in the DL. use OFDM. support TDD and FDD. Support different bandwidths. QoS driven. Both use smart antenna technology (MIMO, STC) Modulation: QPSK, 16QAM, 64QAM in the DL; and BPSK, QPSK, 8PSK and 16QAM in the UL WIMAX VS. LTE Differences: LTE doesn’t require a new network build, an incumbent advantage. Their networks differ in that the eNB is the only network element for LTE, whereas WiMAX has 2, the BS and the ASN. LTE uses single-carrier frequency division multiple access (SCFDMA) for uplink signaling, while WiMax sticks with OFDMA for UL. Frequency bands: WiMAX operates in the 2.3-GHz, 2.5-GHz, 3.5-GHz, and 5.8-GHz frequency bands. LTE operates in 700 & 1700 in NA, 900, 1800, 2600 MHz in Europe; 1800 and 2600 MHz in Asia; 1800 MHz in Australia. An inherent advantage as the lower frequencies offer better penetration. LTE supports seamless passing to cell towers with older network technology such as GSM, CDMAOne, UMTS, and CDMA2000. CONCLUSION LTE and WiMAX are cousins that are developed by two separate entities. LTE-Advanced and 802.16m both fulfill IMT-Advanced requirements. LTE has the incumbent advantage in that a new network doesn’t need to be built out and operates at lower frequencies for better penetration. 4G - The main advantages with 4G are high throughput, low latency, plug and play, FDD and TDD in the same platform, an improved enduser experience and a simple architecture resulting in low operating costs. Main benefit of all IP based network is seamless mobility, which has been the goal of wireless networks for a long time. Seamless mobility describes the ability to move among various radio networks such as WLANS, cellular networks and enterprise networks with no impact to subscriber’s perception of service. REFERENCES Key features of the LTE radio interface, by Erik Dahlman, Anders Furuskär, Ylva Jading, Magnus Lindström and Stefan Parkvall, November 2008 http://www.3gpp.org/LTE Planning of WiMAX and LTE Networks, by Mehrnoush Masihpour and Johnson I Agbinya http://business.motorola.com/experiencelte/pdf/LTEAirInterfaceWhitePaper.pdf http://www.wimax.com/lte/why-the-wimax-vs-lte-battle-isnt-a-battle Exploring Wimax, Award Solutions, Figures 1, 2, 3. 2009. http://blogs.broughturner.com/2010/03/lte-and-spectrum-stupidity.html https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr200811sf5.html http://blogger.xs4all.nl/jurjen1/archive/2008/07/06/400647.aspx http://gigaom.com/2008/03/05/a-little-4g-sibling-rivalry/ http://www.telecomcircle.com/2009/09/what-is-the-difference-between-wimax-and-lte http://www.networkworld.com/news/2010/060710-tech-argument-lte-wimax.html http://www.slideshare.net/marioeguiluz/analysis-wimax-vs-lte http://technologizer.com/2009/05/20/lte-vs-wimax-the-4g-wireless-war/ http://en.wikipedia.org/wiki/4G#Data_rate_comparison http://en.wikipedia.org/wiki/3GPP_Long_Term_Evolution
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