Week #07 Carrier Aggregation

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1 Week #07 Carrier Aggregation
教育部行動寬頻尖端技術人才培育計畫-小細胞基站聯盟中心 示範課程：行動寬頻網路之異質性存取 Week #07 Carrier Aggregation 助理教授：吳俊興 助教：石軒中 國立高雄大學 資訊工程學系

2 Outline Motivation LTE-A and Carrier Aggregation
Component Carriers: PCC and SCC Aggregation Alternatives CA Issues CA in Actions

3 Motivation Carrier Aggregation (CA) is used in LTE-Advanced in order to increase the bandwidth, and thereby increase the bitrate The aggregation is based on R8/R9 carriers to keep backward compatibility with R8 and R9 Ues Carrier aggregation can be used for both FDD and TDD

4 Toward Gigabit LTE

5 CA Examples Carrier aggregation lets mobile operators bond together disparate spectrum bands to add capacity and provide faster data rates in their networks Examples Downlink speeds of up to 225 Mbps have been achieved by aggregating 20 MHz and 10 MHz carriers in the 800 MHz and 1800MHz bands 300Mbps has been delivered by combining two 20 MHz carriers in 1800 MHz and 2.6 GHz bands One trial has combined one 20 MHz block in the 1800 MHz band with two 20 MHz carriers in the 2.6 GHz band to demonstrate peak speeds of 450 Mbps

6 The Road to CA Carrier Aggregation (CA) is introduced in R10
With backward compatibility to R8 to increase the total bandwidth available to UEs and hence their maximum bitrates When CA is used A number of R8 carriers, referred to as Component Carriers (CC), are aggregated Any CA-capable UE can be allocated resources on all CCs, while R8/R9 UEs can only be allocated resources on one CC.

7 Component Carrier Each aggregated carrier is referred to as a component carrier, CC The component carrier can have a bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz and A maximum of five component carriers can be aggregated hence the maximum aggregated bandwidth is 100 MHz In FDD the number of aggregated carriers can be different in DL and UL However, the number of UL component carriers is always equal to or lower than the number of DL component carriers The individual component carriers can also be of different bandwidths For TDD the number of CCs as well as the bandwidths of each CC will normally be the same for DL and UL

8 The Primary Component Carrier (PCC) and Secondary Component Carriers (SCCs)
When carrier aggregation is used there are a number of serving cells, one for each component carrier Different component carriers can be planned to provide different coverage, i.e. different cell size The RRC connection is only handled by one cell, the Primary serving cell, served by the Primary Component Carrier (DL and UL PCC) It is also on the DL PCC that the UE receives NAS information, such as security parameters. In idle mode the UE listens to system information on the DL PCC On the UL PCC PUCCH is sent The other component carriers are all referred to as Secondary Component Carriers (DL and UL SCC), serving the Secondary serving cells The SCCs are added and removed as required, while the PCC is only changed at handover The coverage of the serving cells may differ, for example due to that CCs on different frequency bands will experience different path loss In the case of inter-band carrier aggregation the component carriers will experience different path loss, which increases with increasing frequency Note that for UEs using the same set of CCs, can have different PCC

9 Primary and Secondary Serving Cells
Each component carrier corresponds to a serving cell The different serving cells may have different coverage Carrier aggregation on three component carriers are used for the black UE The white UE is not within the coverage area of the red component carrier

10 Radio Interface to Support Carrier Aggregation

11 Support Serving Cells with Different Timing Advance (TA)
Serving cells with the same TA belongs to the same TA Group (TAG) From R11 it will be possible to handle CA with CCs requiring different timing advance (TA), for example combining CC from eNB with CC from RRH For heterogeneous network planning the use of for example remote radio heads (RRH) is of importance

12 Example of Carrier Aggregation (FDD)
The LTE-Advanced UE can be allocated DL and UL resources on the aggregated resource consisting of two or more Component Carriers (CC) The R8/R9 UEs can be allocated resources on any ONE of the CCs The CCs can be of different bandwidths

13 Scenario of UE with CA

14 Definition of CA Aggregated Channel Bandwidth
Intra-band contiguous Intra-band non-contiguous Inter-band

15 Intra-band and Inter-band Aggregation Alternatives
The spacing between the centre frequencies of two contiguous CCs is Nx300 kHz, N=integer For non-contiguous cases the CCs are separated by one, or more, frequency gap(s)

16 Three Band Allocation for Aggregations
Intra-band contiguous allocation The easiest way to arrange aggregation would be to use contiguous component carriers within the same operating frequency band (as defined for LTE) This might not always be possible, due to operator frequency allocation scenarios. Intra-band non-contiguous allocation The component carriers belong to the same operating frequency band, but have a gap, or gaps, in between Inter-band non-contiguous allocation The component carriers belong to different operating frequency bands

17 Definitions and Notations for CA
CA is initially specified for only a few combinations of E-UTRA operating bands and number of CCs New definitions to specify different CA combinations Aggregated Transmission Bandwidth Configuration (ATBC): total number of aggregated physical resource blocks (PRB) CA Bandwidth Class: indicates a combination of maximum ATBC and maximum number of CCs. In R10 and R11 three classes are defined Class A: ATBC ≤ 100, maximum number of CC = 1 Class B: ATBC ≤ 100, maximum number of CC = 2 Class C: 100 < ATBC ≤ 200, maximum number of CC = 2 CA Configuration: indicates a combination of E-UTRA operating band(s) and CA bandwidth class(es), to exemplify the configuration CA_1C indicates intra-band contiguous CA on E-UTRA operating band 1 and CA bandwidth class C CA_1A_1A, indicates intra-band non-contiguous CA on band 1 with a one CC on each side of the intra-band gap CA_1A_5B indicates inter-band CA, on operating band 1 with bandwidth class A and operating band 5 with bandwidth class B

18 3GPP Releases for CA The increase in bandwidth in LTE-Advanced is provided through aggregation of R8/R9 carriers Keep backward compatibility with R8 and R9 mobiles Carrier aggregation can be used for both FDD and TDD In R10 there are Two component carriers in the DL and Only one in the UL (hence no carrier aggregation in the UL) In R11 there are Two component carriers DL and One or two component carriers in the UL when carrier aggregation is used

19 CA Development of 3GPP Releases
10 Release 11 3GPP 3GPP Release 12 Release 12 Beyond DL intra-Band Contiguous DL inter_Band Maximum 2 DL Carrier Aggregation DL intra-Band non Contiguous 3 DL CA 2 UL CA (inter Band & inter Band non contiguous) FDD+TDD Dual Connectivity LAA (Licensed-Assisted Access) 4 DL CA

20 Changes to R8/R9 for Carrier Aggregation
Introduction of carrier aggregation influences mainly MAC and the physical layer protocol, but also some new RRC messages are introduced In order to keep R8/R9 compatibility the protocol changes will be kept to a minimum Basically each component carrier is treated as an R8 carrier Some changes are required, such as new RRC messages in order to handle SCC MAC must be able to handle scheduling on a number of CCs Major changes on the physical layer are for example that Signaling information about scheduling on CCs must be provided DL as well as HARQ ACK/NACK per CC must be delivered UL and DL

21 Three CA Configurations Defined for R10
Type of CA and  Duplex Type CA Configuration Maximum Aggregated Bandwidth (MHz) Max Number of CC Intra-band contiguous FDD CA_1C 40 2 Intra-band contiguous TDD CA_40C Inter-band  FDD CA_1A_5A 20 1 + 1

22 CA Configurations Defined for R11 and Beyond
In R11 a large number of additional CA configurations are defined The maximum aggregated bandwidth is still 40 MHz and maximum number of CC is 2 For both R10 and R11 any UL CC will have the same bandwidth as the corresponding DL CC Also for inter-band CA there will only be ONE UL CC, i.e. no UL CA Check updated table in the “Carrier Aggregation for LTE” document for each release Type of CA and  Duplex Type CA Configuration Maximum Aggregated Bandwidth (MHz) Max Number of CC Intra-band contiguous FDD CA_1C 40 2 CA_7C TDD CA_38C CA_40C CA_41C Inter-band FDD CA_1A_5A 20 1 + 1 CA_11A_18A 25 CA_3A_5A 30 CA_1A_18A 35 CA_3A_7A Intra-band non-ontiguous FDD CA_25A_25A

23 Examples of CA Combinations

24 CA with Cross-Carrier Scheduling
Cross-carrier scheduling is an important feature in heterogeneous networks Map the Physical DL control channels (PDCCH) on different CCs in the large and small cells The PDCCH, carrying DL Control Information (DCI) with scheduling information, must be received by the UEs at the cell edge PDCCH may be transmitted with higher power than the traffic channels Hence, using different carriers for the PDCCH in the large and small cells reduces the risk of PDCCH interference

25 Example of CA with Cross-Carrier Scheduling

26 CA Scheduling (FDD): Two Main Alternatives
Either resources are scheduled on the same carrier as the grant is received, or so called cross-carrier scheduling may be used

27 CA with Joint Traffic Scheduling

28 Combining CCs from eNBs with CCs from RRHs
From LTE R11 onwards it is possible to handle CA with CCs requiring different timing advance (TA)

29 The Road to CA 拜這幾年通信週邊產品的蓬勃發展，對於行動網路速度的要求越來越高，以Carrier Aggregation(載波聚合)的技術，來滿足使用者對於網速的要求。 然而，最先提出”聚合”概念的，並非在4G時代才出現。幾年前3G的技術應用上 DC-HSDPA （Dual Carrier High Speed Downlink) 就是利用兩個載波,透過聚合的方式，可獲得兩倍的下載速率 (21Mbps 42Mbps) 。 至於CDMA2000的EVDO Rev.B 也是透過類似的方式來達到網路的提升 (3.1Mbps6.2Mbps)

30 Conditional CA 小封包的傳送，通常不會啟動CA

31 CA Deployment Conditions
Carrier Aggregation的滿足條件: (以目前台灣發展進度) CoSite (同一站台同時有該業者的多頻段設備) Parameter設定 手機對應 下載流量大才會啟用

32 CA and DC-HSDPA Dual Cell (DC-)HSDPA is the natural evolution of HSPA by means of carrier aggregation in the downlink UMTS licenses are often issued as 10 or 15 MHz paired spectrum allocations The basic idea of the multicarrier feature is to achieve better resource utilization and spectrum efficiency by means of joint resource allocation and load balancing across the downlink carriers An advanced HSPA network can theoretically support up to 28 Mbit/s and 42 Mbit/s with a single 5 MHz carrier for Rel7 (MIMO with 16QAM) and Rel8 (64-QAM + MIMO), in good channel condition with low correlation between transmit antennas An alternative method to double the data rates is to double the bandwidth, i.e. 10 MHz by using DC-HSDPA New HSDPA UE categories have been introduced that support DC-HSDPA DC-HSDPA can support up to 42Mbit/s and it does not need to rely on MIMO transmission

33 CA Issues – Channel Spacing

34 CA Issues – Transmitter Characteristics

35 CA Issues - Conditions to Activate and Deactivate SCCs
MAC必須依據不同情況來控制各SCC之激活與去激活，必須注意的是PCC無法被MAC層去激活，SCC則能由MAC彈性控制，並使用邏輯通道辨識碼（Logical Channel ID = 11011）來控制不同輔載波。 當下面兩個條件同時成立時，則輔載波滿足激活條件：  當用戶所有的queues超過ㄧ鄰界值（threshold）時，亦即有大量資料傳輸需要傳輸。  大量資料傳輸需求需持續一段時間，該條件為避免乒乓（ping-pong）效應。 當滿足下列其中一條件且持續一段時間後，則輔載波滿足去激活條件：  當用戶所有的queues低於ㄧ鄰界值（threshold）時，亦即有無大量資料傳輸需要傳輸。 SCC之通道訊號品質低於定義之鄰界值時。 藉由上述條件，eNodeB會發送激活或去激活需求（Activation/Deactivation Request）給MAC層，MAC將依據該資訊對不同輔載

36 Steps of Adding a Second Carrier

37 CA Issues - Handover

38 Handover Example  用戶裝置支援CA且載波聚合配置為PCC為B1，SCC為B2。
 用戶移動至B1覆蓋範圍較弱區域，此時異頻量測（inter-frequency measurements）開始執行， 且PCC換手至B2，B1不在服務範圍內，則根據基地台排程設計，可能配置為SCC為B1亦或是不被配置使用，即使B1配置成功，也可能因為訊號狀況差，不被激活使用。  用戶移動至位子3時，執行同頻（intra-frequency）換手，此時PCC保持為B2。  移動至位子4後，B1會根據基地台排程可能被分配為SCC，並可能激活載波聚合功能。

39 Band Allocations of Taiwan Operators

40 CA Combinations for Taiwan Operators
由此表可以瞭解，國內各電信業者目前所擁有的頻寬大小，透過前面提到的Carrier Aggregation技術， 各業者可將各頻段的頻寬合併後使用，各業者目前目前可使用的頻率如下 中華電信: ( ) =40Mbps 台哥大: (20+10)=30Mbps 遠傳:700+( )=43Mbps 亞太(目前漫遊台哥大的網路) 台灣之星:(10+20)=30Mbps

41 Possible CA Configurations for Taiwan Operators
中華電信的載波聚合組合 Band 3+7 ＆ 3+8 台灣大哥大的載波聚合組合 Band 3+28 遠傳的載波聚合 Band 3+7 、3+28、3+38(FDD+TDD)、7+38 台灣之星可使用 7+8 (3CA) 中華電信的載波聚合 3+7+8 遠傳的載波聚合

42 Summary CA lets mobile operators bond together disparate spectrum bands to add capacity and provide faster data rates in their networks Technical fundaments Component Carriers: PCC and SCC Aggregation combinations CA Issues for deployments