LTE Curs 1 _v2012
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Transcript of LTE Curs 1 _v2012
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LTE for 4G Mobile Broadband
by Ren ANDREESCUCurs 1
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LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCUA set of several frequencies are used in one cell and other mutually exclusive
sets are used in other cells in the cluster. This arrangement forces one to examine the
criteria as to when a frequency can be reused again.
The figure provides an example of the popular 7-cell cluster arrangement, with six clusters surrounding a cluster in
the middle. In the middle of each cluster is a base station that must have the same
frequency set if the network is being built with the 7-cell cluster as the basis.
It can be shown that if the cluster size is N and the cell radius is R, the reuse
distance D is given by D = R (3N)1/2.
The cluster sizes need not be the same throughout the network. Cells can be split
to provide increased capacity (number of subscribers per square area) towards city
centers.
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LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCU -
LTE for 4G Mobile Broadband
by Ren ANDREESCUFlat Architecture of LTE and SAE ( System Architecture Evolution )
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LTE for 4G Mobile Broadband
by Ren ANDREESCULTE Network Architecture
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LTE for 4G Mobile Broadband
by Ren ANDREESCULTE Network Architecture
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LTE for 4G Mobile Broadband
by Ren ANDREESCULTE Specifications
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LTE for 4G Mobile Broadband
by Ren ANDREESCUMultiple access scheme
DL: OFDMA with CP.
UL: Single Carrier FDMA (SC-FDMA) with CP.
Adaptive modulation and coding
DL modulations: QPSK, 16QAM, and 64QAM
UL modulations: QPSK and 16QAM
Rel-6 Turbo code: Coding rate of 1/3, two 8-state constituent encoders, and a contention-free internal interleaver.
Advanced MIMO spatial multiplexing techniques
(2 or 4)x(2 or 4) downlink and uplink supported.
Multi-layer transmission with up to four streams.
Multi-user MIMO also supported.
ARQ within RLC sublayer and Hybrid ARQ within MAC sublayer.
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LTE for 4G Mobile Broadband
by Ren ANDREESCULTE Frame Structure
Two radio frame structures defined.
Generic frame structure: FDD and TDD.
Alternative frame structure: TDD only.
Generic radio frame has duration of 10 ms. It consists of 20 slots.
A slot has a duration of 0.5 ms. 2 slots comprise a subframe.
A resource block (RB) spans 12 subcarriers over a slot duration
of 0.5 ms. One subcarrier has bandwidth of 15 kHz.
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LTE for 4G Mobile Broadband
by Ren ANDREESCUPeak data rate
100 Mbps DL/ 50 Mbps UL within 20 MHz bandwidth.
Up to 200 active users in a cell (5 MHz)
Less than 5 ms user-plane latency
Mobility
Optimized for 0 ~ 15 km/h.
15 ~ 120 km/h supported with high performance.
Supported up to 350 km/h or even up to 500 km/h.
Enhanced multimedia broadcast multicast service (E-MBMS)
Spectrum flexibility: 1.25 ~ 20 MHz
Enhanced support for end-to-end QoS
Requirements of LTE
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LTE for 4G Mobile Broadband
by Ren ANDREESCUSubcarrier Mapping
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LTE for 4G Mobile Broadband
by Ren ANDREESCUSubcarrier Mapping
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LTE for 4G Mobile Broadband
by Ren ANDREESCULTE Frequency Bands
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LTE for 4G Mobile Broadband
by Ren ANDREESCULTE Downlink - OFDM
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LTE for 4G Mobile Broadband
by Ren ANDREESCUSingle Carrier with Frequency Domain Equalization
SC/FDE delivers performance similar to OFDM with essentially
the same overall complexity, even for long channel delay.
SC/FDE has advantage over OFDM in terms of:
Low PAPR.
Robustness to spectral null.
Less sensitivity to carrier frequency offset.
Disadvantage to OFDM is that channel-adaptive subcarrier bit
and power loading is not possible.
Single Carrier FDMA (SC-FDMA) is an extension of SC/FDE to accommodate multiple-user access.
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LTE for 4G Mobile Broadband
by Ren ANDREESCUBandwidth Configuration
The transmission bandwidth configuration in MHz is given as:
where = 15 kHz is the subcarrier spacing.
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LTE for 4G Mobile Broadband
by Ren ANDREESCUSC-FDMA and OFDMA
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LTE for 4G Mobile Broadband
by Ren ANDREESCUSC-FDMA and OFDMA
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LTE for 4G Mobile Broadband
by Ren ANDREESCULTE Bandwidth / Resource COnfiuration
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LTE for 4G Mobile Broadband
by Ren ANDREESCULTE Frame Structure Type 1
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LTE for 4G Mobile Broadband
by Ren ANDREESCUSystem Capacity
The SINR in an OFDM system is approximatted , so the capacity is:
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LTE for 4G Mobile Broadband
by Ren ANDREESCUCapacity gains
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LTE for 4G Mobile Broadband
by Ren ANDREESCUThe Basic assumption is: for less then 10% ISI there is no
need for equalization, and a simple detection can be done.
For the 2-3GHz band, a 10sec delay spread can be assumed,
the basic carrier spacing should be approximately 4KHz
(adding on top of that the Guard Interval).
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LTE for 4G Mobile Broadband
by Ren ANDREESCUFrequency Division Duplexing (FDD) Principles
One Frequency is Used for the DownLink, Using OFDM/TDM .
A Second Frequency is Used for the UpLink , Using OFDMA/TDMA .
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LTE for 4G Mobile Broadband
by Ren ANDREESCUOFDMA/TDMA Principles
Using OFDMA/TDMA, Sub Channels are allocated in the Frequency Domain, and OFDM Symbols allocated in the Time Domain.
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LTE for 4G Mobile Broadband
by Ren ANDREESCUUpLink OFDMA Symbol
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LTE for 4G Mobile Broadband
by Ren ANDREESCUUsing Special Permutations for Carrier Allocation
All usable carriers are divided into 23 carrier groups named basic group, each main group contains 23 basic groups.
There are 3 main groups.
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LTE for 4G Mobile Broadband
by Ren ANDREESCUUsing Special Permutations for Carrier Allocation
Carriers are allocated by a basic series and its cyclic permutations
Basic Series:
0,5,2,10,4,20,8,17,16,11,9,22,18,21,13,19,3,15,6,7,12,14,1
After two cyclic permutations we get:
2,10,4,20,8,17,16,11,9,22,18,21,13,19,3,15,6,7,12,14,1,0,5
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LTE for 4G Mobile Broadband
by Ren ANDREESCUThe effect of multipath channel on each of the subcarriers can be viewed in frequency domain
For the th subcarrier the received and demultiplexed sample value, Y(k), is given by Y(k) = X(k)* H(k), where H(k) is the frequency response of the th subchannel
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LTE for 4G Mobile Broadband
by Ren ANDREESCUWe begin by grouping L data symbols into a block known as an OFDM symbol. An OFDM symbol lasts for a duration of T seconds,
where T = LTs.
In order to keep each OFDM symbol independent of the others after going through a wireless channel, it is necessary to introduce a guard
time between OFDM symbols:
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LTE for 4G Mobile Broadband
by Ren ANDREESCUThis way, after receiving a series of OFDM symbols, as long as the guard time Tg is larger
than the delay spread of the channel, each OFDM symbol will interfere only with itself:
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LTE for 4G Mobile Broadband
by Ren ANDREESCUOFDM synchronization in (a) time and (b) frequency. Here, two subcarriers in the time domain and eight subcarriers in the frequency domain are shown, where fc = 10 MHz, and the subcarrier spacing f = 1 Hz