4g Lte

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  • Topic: Radio resource management, Modulation, Protocol data unit
  • Pages : 29 (8123 words )
  • Download(s) : 47
  • Published : April 28, 2013
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LTE
 Network
 Architecture
 
1. Support only a Packet-switched (PS) service (seamless IP connectivity) 2. Overview

3.

Core Network: l PCRF (Policy Control and Charging Rules Function): • Policy control decision-making • Flow-based charging control • Provide QoS authorization l GMLC (Gateway Mobile Location Center):Send position requests to MME and receives the final location estimates l HSS (Home subscriber server):

l

l

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Contains users’ SAE subscription data (e.g. EPS subscribed QoS profile & access restrictions) • Holds information about PDN to which user can connect P-GW (PDN Gateway): • IP address allocation for the UE • QoS enforcement • Flow-based charging • Filtering of downlink user IP packets into different QoS-based bearers • Transport level QoS mapping/marking S-GW (Serving Gateway): • 用户数据包通过 S-GW 发送,当用户在 eNodeB 之间移动式,S-GW 作为数据承载的 本地移动性管理实体。 • 保留承载(bearers)信息并临时把下行数据存储在缓存区里,以便当 MME 开始寻呼 UE 时重新建立承载 • administrative functions: collecting information for charging/ volume of data send and receive from the user/ legal interception • Packet routing and forwarding • Transport level QoS mapping/markin MME (Mobile Management Entity): the control node which processes the signaling between the UE • and the CN

4.

• Bearer management: establishment, maintenance and release • Connection management: establishment, security • MME selection for inter-MME handover • Involved only on the control plane (CP) • NAS signaling and its security • AS Security Control • Tracking Area List Management • PDN GW and Serving GW selection • Roaming and Authentication Access Network (radio part) —E-UTRAN (simply consists of a network of eNodeBs) l Home eNodeB(HeNB): 1) can be used in customers’ premises 2) Enhancing of the network coverage and/or capacity l eNodeB: • Radio resource management • E-UTRAN synchronization & interference control • IP header compression • Encryption/ Integrity protection of user data (security) • MME selection • Routing of user plane data from/to S-GW 承载路径的建立 l S1 interface: • many-to many • between eNB and EPC (MME/S-GW/P-GW)

5.

• support network sharing. redundancy, loading balancing l X2 interface: • Used for inter eNB handover, loading balancing and interference coordination • Logical interface --- usually route via the same transport as S1 interface • Normally used for control plane information, nut during the handover it can be temporarily for user data forwarding. • X2 is also used to carry interference level information which is used for load and interference management eNodeB architecture: basedband+ Remote Radio Head(RRH) *Radio has moved from the baseband portion and will eventually merge with antennas *Advantages of RRH: • Baseband part requires less space which leads to lower rental costs • Closeness of the radio part to the antenna reduces cable power loss by about 3 dB *dB = 10logX 0 dBm = 10log1 mw; 0 dBw = 10log1 W = 10log1000 mw = 30 dBm

Communication
 System
 Review
 
1. BPSK • spectral efficiency(uncoded)= 1 bps/Hz • the most reliable modulation scheme: High data integrity Requires low SNR to decode • longest cell range at the price/low spectral efficiency • not used for data in LTE 2. QPSK • Modulation spectral efficiency = 2 bps/Hz • Data rate doubled compared to BPSK • used in LTE 3. 16 QAM • Modulation spectral efficiency = 4 bps/Hz • Requires moderate to high SNR 4. 64 QAM • Modulation spectral efficiency is = 6 bps/Hz • Requires high SNR • The highest modulation order used in LTE *Higher order modulation schemes highest spectral efficiency (More bits/symbol) Require higher signal quality (SNR) to demodulate Reduced range *Control signaling typically uses BPSK or QPSK with low code rate

! S$ 5. Shannon Capacity:
  C = W log 2 #1+ & " N%
Capacity/Rate BW

[ bits/second ]

snr
 (linear
 scale)
  SNR
 (log
 scale)
  SNR=10lg(snr)
 

6. AMC (Adaptive Modulation and Coding) • Modulation and code...
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