3G Evolution. High data rates in mobile communication. Outline. Chapter: Rate control [stefan Parkval] Rate control or power control [stefan Parkval]

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1 hapter: 3G Evolution 3 High data rates in moile communication Payam Amani Payam.Amani@eit.lth.se Department of Electrical and Information echnology Outline High data rates: Fundamental constraints High data rate in interference limited High data rates in noise limitted Higher data rates within a limited andwidth : Higher order modulation Higher order modulation in comination with channel coding Variations in instantaneous transmit power Wider andwidth including multi-carrier transmission 3/19/ /19/9 3G Evolution - HSPA and LE for Moile Broadand ate control or power control [stefan Parkval] ate control [stefan Parkval] 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 3 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 4

2 Higher data rates Higher data rates: Fundamental constraints Higher end user data rates compared to first 3G standards: one of the main targets for LE What do we mean y high data rates? Higher peak data rates Higher data rates over the entire cell area Higher data rates on the cell edge Shannon channel capacity: hannel only impared y additive white Gaussian noise Main factors limiting the channel capacity: Availale signal power to noise power ratio Bandwidth S = BW log 1 + S E = + BW log = + 1 BW log 1 BW E γ = BW E γ log(1 + γ E min ) γ 1 = γ 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 5 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 6 Higher data rates: Fundamental constraints Minimum required E/ at receiver as a function of andwidth utilization Information rate cannot exceed channel capacity. adio link andwidth utilization γ. Lower ound on the required received energy per information it, normalized to the noise power density for a given andwidth utilization. S = BW log 1 + S E = + BW log = + 1 BW log 1 BW E γ = BW E γ log(1 + γ E min ) γ 1 = γ Bandwidth utilization significantly smaller than one : elatively constant minimum required E/ regardless of andwidth utilization. Bandwidth utilization larger than one (constant and andwidth): E/ increases rapidly y andwidth utilization. Increase in data rate: much larger increase in the minimum required signal power at receiver. 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 7 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 8

3 Minimum required E/ at receiver as a function of andwidth utilization 5 Minimum required E / at the receiver as a function of andwidth utilization Power Limited egion Bandwidth Limited egion High data rates in noise-limited When noise is the main source of radio-link impairment: Increase of achievale data rates in a given andwidth requires at least the same relative increase of signal power. Minimum required E / (db) Bandwidth Utilization γ Low andwidth utilization: Power limited operation : increase in the availale andwidth does not sustantially impact what received signal power is required for a certain data rate. High andwidth utilization Bandwidth limited operation : Furthere increase in data rate requires a much larger relative increase in the receive signal power unless the andwidth is increased in proportion to the increase in the data rate. 3/19/9 March 19th, 9 3G Evolution - HSPA and LE for Moile Broadand 9 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 1 High data rates in noise-limited High data rates in noise-limited o make use of the availale S efficiently; transmission andwidth should at least e the same order as the data rate to e provided. By reducing the range in theory we can provide higher data rates. equiring andwidth efficiency greater or equal to one leads to significant cell range reduction. High data rates only availale for centre of the cell. How to increase overal received signal power for a given transmit signal power? Add antennas to the receiver side (eceiver antenna diversity)+ proper comining an increase the signal to noise ratio after comining in proportion to the numer of antennas. Allows for larger data rates for the same cell range. Add antennas to the transmitter (typically ase station); focus a given total transmit power in the direction of the receiver (eam forming). an increase signal power and allow for higher data rates for the same cell range. SIMO-MISO SIMO-MISO 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 11 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 1

4 High data rates in noise-limited eceive diversity SIMO case SIMO and MISO efficiently provide higher data rates up to a certain level (saturation), i.e as long as the data rates are power limited rather than andwidth limited. he mentioned saturation can e avoided y means of spatial multiplexing or. Details in chapter 6. Alternatively one can reduce noise power y designing a more advanced receiver with a smaller noise figure. SIMO-MISO SIMO-MISO Addition of receiver antenna yields only a logarithmic increase in channel capasityin SIMO channels. Knowledge of channel information at the transmitter provides no capacity enefits. SIMO h s = log 1 h F i E + = 1, i = 1,,..., M log 1 E + = s SIMO M 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 13 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 14 ransmit diversity MISO case In case of acense of channel knowledge in transmitter there is no enefit for MISO channels over SISO channels in sence of capacity. However in fading environment there is some enefits for MISO over SISO. If the channel is known to the transmitter the capacity is similar to the SIMO case. MISO hannel unknown to transmitter = log 1 E + s MISO h F M if h i MISO = 1( i = 1,,..., M E = log(1 + s ) ) system system : hannel has no prefered direction and is completely unknown to the transmitter ss = I M. Signals are independent and equi-powered at the transmit antennas. Es y = Hs + n M = log det I M Es + HH M H hannel known to transmitter log 1 E + s h MISO = F Orthogonal channels maximize capacity Es = M log(1 + ) M = M = M, H i, j = 1, H F = M 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 15 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 16

5 Higher data rates in interference limited Higher data rates in interference limited Dominant source of link impairment in moile communications is usually inter-cell or intra-cell interference. Similar results to the noise limited. Interference is usuall structured and can e suppressed y means of spatial processing. Maximum achievale data rates in a given andwidth is limited y availale SI. 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 17 o achieve higher data rates: educe cell size, reduce numer of users, reduce the overal trafic in the cell, reduce the interference level in the cell. of the received signals in SIMO case increases SI after antenna comining. Beam forming in MISO case will focus the transmit power in the direction of the target receiver thus reduces the interference to other radio links, thus improves overal SI in the system. 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 18 Higher data rates within a limited andwidth Higher order modulation Providing data rates larger than the availale andwidth is fundamentally inefficient. Bandwidth is a scares and expensive resource. In some in moile communication high S and high SI can e made availale (users near centre of cell and small cells with low traffic). Signal onstellations for Higher order Modulations Increasing the modulation alphaet to send more its per modulation symol. QPSK in first 3G systems. Bandwidth of transmitted symol is in principle independent of order of modulation and mainly depends on modulation rate. Bandwidth utilization of 16QAM and 64QAM are and 3 times of QPSK. (less roust to noise and interference) LE shall support providing high data rates in a limited andwidth for users in such conditions. 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 19 3/19/9 3G Evolution - HSPA and LE for Moile Broadand

6 An application: Higher order modulation in comination with channel coding In general, 16QAM and 64QAM require higher received E/ for a given BE compared to QPSK. By means of channel coding sometimes 16QAM or 64QAM require less E/ for a given BE compared to QPSK. (in cases that the target andwidth utilization implies that with lower order modulation no or very little coding gain can e achieved.) For a given S/SI a certain comination of modulation scheme and channel coding rate is optimal in sence of providing highest andwidth utilization. IPV over WiMAX: Key Success Factors, challenges, and Solutions ommunications Magazine, IEEE. vol. 45, pp.87-93, August 7. 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 1 3/19/9 3G Evolution - HSPA and LE for Moile Broadand Variations in instantaneous transmit power Wider andwidth including multi-carrier transmission: In case of higher modulation order + coding we will have larger variations in amplitude of the modulated signal and thus higher instantaneous power peaks. Increase the dynamical range of the power amplifier. eduction in power amplifier efficiency and more expensive to uild. eduction of mean transmit power (smaller cells) More suitale for downlink than uplink. Same average power ransmission andwidth at least as large as the required data rates is needed to provide high data rates as efficiently as possile in terms of required S/SI. Providing high data rates + good coverage is one of the main aims of LE support for wider transmission andwidth. Spectrum is scarce and expensive omplex radio equipment (sampling rates, DA and AD complexity and power consumption and signal processing complexity, more complex and expensive F parts.) 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 3 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 4

7 Wider andwidth including multi-carrier transmission: Signal corruption due to time dispersion Multipath propagation A snapshot of hannel frequency response Wider andwidth including multi-carrier transmission: Dependent on propagation environment. Small cells and rural areas have less frequency selectivity. A snapshot of hannel frequency response ime dispersive channel non- constant frequency response of the channel (frequency selectivity). Larger impact for wideand transmissions. Frequency eceiver side equalization used to conteract signal corruption due to radiochannel frequency selectivity. Shown good results till 5MHz transmission andwidth. Frequency Higher andwidth : very complicated equalizers. 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 5 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 6 Wider andwidth: Options: Usage of less optimal equalization worse radio link performance Use special transmission schemes and signal designs : Multicarrier transmission: Provides very smooth evolution in terms of oth radio equipment and spectrum of an existing radio- access technology to wider transmission andwidth and corresponding possiility for higher data rates especially for downlink. Backward compatiility. Multi-carrier transmission: transmitting overal wider-and signal as several more narrowand frequency- multiplexed signals such as OFDM. More discussed in chapter 4. Use of specific wider-and single carrier schemes such as DFS- OFDM more discussed in chapter 5. 3/19/9 March 19th, 9 3G Evolution - HSPA and LE for Moile Broadand 7 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 8

8 heoretical WDMA spectrum efrences : Spectrum shaping increases the spectrum from its theoretical value. Spectrum widenning due to the transmitter imperfections. Avoid inter-sucarrier interference (can e accepted to some level). Large variations in the instantaneous transmit power. Inefficient power amplifier. More suitale for downlink. 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 9 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 3 Questions: hanks for your attention : Questions? 3/19/9 3G Evolution - HSPA and LE for Moile Broadand 31