1. LTE-Advanced (Long Term Evolution-Advanced)
國立屏東科技大學 資訊管理系
教材編撰：童曉儒 教授
林美賢

2. 章節要點 (Chapter keys) LTE-Advanced Overview Main New Functionalities
Carrier Aggregation
Carrier Aggregation Alternatives
Possible Carrier Aggregation scenarios
MIMO, Multiple Input Multiple Output – or spatial multiplexing
Relay Nodes
Coordinated Multi Point operation (CoMP)-R11
Benefits of LTE-A compared with LTE

3. 章節目錄 (Chapter layouts)
LTE-Advanced Overview 1 2
Main New Functionalities 3
Carrier Aggregation 4
Carrier Aggregation Alternatives 5
Possible Carrier Aggregation scenarios 6
MIMO, Multiple Input Multiple Output – or spatial multiplexing
Relay Nodes 7
Coordinated Multi Point operation (CoMP)-R11 8 9
Benefits of LTE-A compared with LTE

4. Overview LTE-Advanced: 3GPP Release10
Fulfill the requirements set by ITU for IMT Advanced, also referred to as 4G.
Release 8 LTE
Release 10 LTE-A
IMT-Advanced target
Peak data rate
Downlink
300Mbps
3Gbps
1Gbps*
Uplink
75Mbps
1.5Gbps
Peak spectrum efficiency [bps/Hz] 15
(4x4 MIMO) 30
(8x8 MIMO)
3.75
(64QAM SISO)
6.75
(2x4 MIMO)
In LTE-Advanced focus is on higher capacity:The driving force to further develop LTE towards LTE–Advanced - LTE Release10 was to provide higher bitrates in a cost efficient way and, at the same time, completely fulfil the requirements set by ITU for IMT Advanced, also referred to as 4G.
- Increased peak data rate, DL 3 Gbps, UL 1.5 Gbps
- Higher spectral efficiency, from a maximum of 16bps/Hz in R8 to 30 bps/Hz in R10
- Increased number of simultaneously active subscribers
- Improved performance at cell edges, e.g. for DL 2x2 MIMO at least 2.40 bps/Hz/cell.
8x8 MIMO in the DL and 4x4 in the UL
LTE-Advanced: 3GPP Release10. 由3GPP發布的第10版.
Fulfill the requirements set by ITU for IMT Advanced, also referred to as 4G. 它所設定的目標是由國際的電信組織ITU所制定的IMT Advanced，希望可以達到4G的標準。
*MIMO = multiple input multiple output 多輸入多輸出（多重天線）
* 100Mbps for high mobility and 1Gbps for low mobility

5. Main New Functionalities
The main new functionalities introduced in LTE-Advanced are Carrier Aggregation (CA), enhanced use of multi-antenna techniques and support for Relay Nodes (RN).
Carrier Aggregation(頻段累加):頻段可切換，例如4G手機也能使用3G頻段。
MIMO(多重天線):提升系統乘載量。
Enhanced ICIC:兩個基地台可互相協調，以解決干擾的問題。
Relaying(轉送):可無線擴充的基地台。
Enhanced SC-FDMA:更省電，更能抵抗雜訊干擾。

6. Carrier Aggregation
Each aggregated carrier is referred to as a component carrier (have a bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz)
A maximum of five component carriers can be aggregated. Hence the maximum bandwidth is 100 MHz.
The number of aggregated carriers can be different in DL and UL.
Each aggregated carrier is referred to as a component carrier. 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 bandwidth is 100 MHz. The number of aggregated carriers can be different in DL and UL, however the number of UL component carriers is never larger than the number of DL component carriers. The individual component carriers can also be of different bandwidths, see figure 1.
假設每個頻段載波都是一個元件(Component carrier)，元件根據需要組合後可以產生出想要的頻段。
(可以建立出 1.4, 3, 5, 10, 15 or 20 MHz)
最多可以有5個元件來組成，最高頻寬可達100MHz。
下為Component carrier 示意圖:

7. Carrier Aggregation Aggregation of R8/R9 carriers.
Carrier aggregation enables spectrum flexibility by aggregating smaller non-contiguous bandwidths.
By combining blocks of spectrum known as component carriers (CC), carrier aggregation enables the use of fragmented spectrum and allows LTE-A to meet its IMT-Advanced headline data rate of 1 Gbps.
Carrier aggregation is achievable by a hardware upgrade, and is backward compatible with 3GPP Release 8. Carrier aggregation enables spectrum flexibility, but it is not just about multiple 20 MHz component carriers—there is also the ability to aggregate smaller non-contiguous bandwidths. In this way, the bandwidth can even be changed dynamically to accommodate the needs of individual users. However, achieving carrier aggregation in devices in the real world presents a real challenge.
如下圖不同的裝置可以彈性使用不同的整合頻段。

8. Carrier Aggregation Alternatives
Intra-band contiguous allocation
non-contiguous allocation: intra-band or inter-band
The easiest way to arrange aggregation is to use contiguous component carriers within the same operating frequency band (as defined for LTE), so called intra-band contiguous. This might not always be possible, due to frequency allocation scenarios. For non-contiguous allocation it could either be intra-band, i.e. the component carriers belong to the same operating frequency band, but are separated by a frequency gap, or it could be inter-band, in which case the component carriers belong to different operating frequency bands
Intra-band,contiguousvu: 相同頻段的CC整合 。
Intra-band,non-contiguous:相同頻段但不良續的CC整合。
Inter-band,non-contiguous:不同頻段的CC整合。
一個單位的載波=一個細胞(如圖的eNodeB)不同的Band(圖中的圈圈)的範圍不一定一樣。

9. A component carrier=a serving cell
A component carrier=a serving cell. The different serving cell may have different coverage.
Carrier aggregation on all three component carriers is only possible for the black UE.
The white UE is not within the coverage area of the red component carrier.
When carrier aggregation is used there is a number of serving cells, one for each component carrier. The coverage of the serving cells may differ – due to e.g. component carrier frequencies. The RRC connection is handled by one cell, the Primary serving cell, served by the Primary component carrier (DL and UL PCC). The other component carriers are all referred to as Secondary component carrier (DL and possibly UL SCC), serving the Secondary serving cells. In the inter-band CA example shown in figure 3, carrier aggregation on all three component carriers is only possible for the black UE, the white UE is not within the coverage area of the red component carrier.
Introduction of carrier aggregation influences mainly MAC and the physical layer protocol, but also the RLC buffer must be larger and RRC must be able to make decisions about addition/removal of secondary CC.
藍色為主要的Serving Cell 綠色紅色為次要 裝置會先使用藍色頻段，當不夠使用時才會去使用次要頻段。

10. Possible Carrier Aggregation scenarios
Three possible aggregation application scenarios.
(a) The lower frequency f1 (shown in grey) is used to increase coverage and f2 (shown in blue) is used to boost the data rate (f2 > f1);
(b) Both frequencies are used to increase cell throughput; and
(c) f1 provides macro coverage and f2 is used to boost throughput in hotspots.
Figure 3 shows three of the many possible LTE-Advanced carrier aggregation application scenarios. In Figure 3(a), the lower frequency f1 is used to increase coverage while f2 is used to boost the data rate. Figure 3(b) demonstrates the use of both frequencies to increase cell throughput; and in Figure 3(c) f1 provides macro coverage and the higher frequency f2 is used to boost throughput in hotspots.
(a)灰色區域f1是用來增加覆蓋率而藍色區域
f2是用來增加資料傳輸速率(速率f2>f1)。
(b)兩個頻段都是用來增加覆蓋率。
(c) 灰色區域f1是用來增加覆蓋率藍色區域f2
是用來增加結點傳輸量，較有彈性。

11. MIMO, Multiple Input Multiple Output – or spatial multiplexing
MIMO : transmission of two (or more) different data streams on two (or more) different antennas - using the same resources in both frequency and time, separated only through use of different reference signals - to be received by two or more antennas.
MIMO  is used to increase the overall bitrate through transmission of two (or more) different data streams on two (or more) different antennas - using the same resources in both frequency and time, separated only through use of different reference signals - to be received by two or more antennas.
如下圖，如果藍色和紅色使用不同頻率傳輸，則就有加成的效果。

12. MIMO LTE-Advanced: 8x8 MIMO in the DL and 4x4 in the UL.
MIMO can be used when S/N (Signal to Noise ratio) is high, i.e. high quality radio channel.
When S/N is low, it is better to use TX-diversity.
One or two transport blocks are transmitted per TTI. A major change in LTE-Advanced is the introduction of 8x8 MIMO in the DL and 4x4 in the UL. MIMO can be used when S/N (Signal to Noise ratio) is high, i.e. high quality radio channel. For situations with low S/N it is better to use other types of multi-antenna techniques to instead improve the S/N, e.g. by means of TX-diversity.
LTE-Advanced中下行允許8x8的天線，上行允許4x4的天線。
MIMO再訊號(Signal to Noise ratio,S/N)較好的時候可以盡量發揮它的傳輸效能。
當再訊號比較弱的時候以TX-diversity方式(多重傳送)來傳輸訊號會較強。
MIMO速度較快，TX-diversity訊號較強。

13. Relay Nodes
The Relay Nodes: low power base stations that will provide enhanced coverage and capacity at cell edges, and hot-spot areas and it can also be used to connect to remote areas without fiber connection.
In LTE-Advanced, the possibility for efficient heterogeneous network planning – i.e. a mix of large and small cells - is increased by introduction of Relay Nodes (RNs). The Relay Nodes are low power base stations that will provide enhanced coverage and capacity at cell edges, and hot-spot areas and it can also be used to connect to remote areas without fibre connection. The Relay Node is connected to the Donor eNB (DeNB) via a radio interface, Un, which is a modification of the E-UTRAN air interface Uu. Hence in the Donor cell the radio resources are shared between UEs served directly by the DeNB and the Relay Nodes. When the Uu and Un use different frequencies the Relay Node is referred to as a Type 1a RN, for Type 1 RN Uu and Un utilize the same frequencies, see figure 7. In the latter case there is a high risk for self interference in the Relay Node, when receiving on Uu and transmitting on Un at the same time (or vice versa). This can be avoided through time sharing between Uu and Un, or having different locations of the transmitter and receiver. The RN will to a large extent support the same functionalities as the eNB – however the DeNB will be responsible for MME selection. 

14. UEs at the edge of the donor cell are connected to the RN via Uu.
The Relay Node (RN) is connected to the DeNB via the radio interface Un.
UEs at the edge of the donor cell are connected to the RN via Uu.
The frequencies used on Un and Uu can be different, outband, or the same, inband. In the inband case there is a risk for self interference in the RN.
The Relay Node (RN) is connected to the DeNB via the radio interface Un. UEs at the edge of the donor cell are connected to the RN via Uu, while UEs closer to the DeNB are directly connected to the DeNB via the Uu interface. The frequencies used on Un and Uu can be different, outband, or the same, inband. In the inband case there is a risk for self interference in the RN.
Relay node是透過無線的方式來與Macro cell 基地台相連。
如下圖DeNB以無線方式連結至Relay Node(RN)再連結至手機，兩者的頻率可以相同。

15. Coordinated Multi Point operation (CoMP) – R11
CoMP: Improve network performance at cell edges.
A number of TX (transmit) points provide coordinated transmission in the DL, and a number of RX (receive) points provide coordinated reception in the UL.
CoMP can be done for both homogenous networks as well as heterogeneous networks.  
The main reason to introduce CoMP is to improve network performance at cell edges. In CoMP a number of TX (transmit) points provide coordinated transmission in the DL, and a number of RX (receive) points provide coordinated reception in the UL. A TX/RX-point constitutes of a set of co-located TX/RX antennas providing coverage in the same sector. The set of TX/RX-points used in CoMP can either be at different locations, or co-sited but providing coverage in different sectors, they can also belong to the same or different eNBs. CoMP can be done in a number of ways, and the coordination can be done for both homogenous networks as well as heterogeneous networks.  In figure 8 two simplified examples for DL CoMP is shown. In both these cases DL data is available for transmission from two TX-points. When two, or more, TX-points, transmit on the same frequency in the same subframe it is called Joint Transmission.  When data is available for transmission at two or more TX-points but only scheduled from one TX-point in each subframe it is called Dynamic Point Selection. For UL CoMP there is for example Joint Reception, a number of RX-points receive the UL data from one UE, and the received data is combined to improve the quality. When the TX/RX-points are controlled by different eNBs extra delay might be added, since the eNBs must communicate, for example in order to make scheduling decisions. When CoMP is used additional radio resources for signaling is required e.g. to provide UE scheduling information for the different DL/UL resources.
CoMP是為了提升網路邊緣的細胞效能。
用多個基地台的信號來互相協調傳輸以提升上下行訊號強度。

16. DL CoMP :
a) Joint Transmission;  two TX-points transmit to one UE in the same radio resource.
b) Dynamic Point Selection; two TX points are ready to transmit, but only one will be scheduled in each subframe.
DL CoMP:
a)Joint Transmission:兩個基地台同時傳送一樣的信號以達到加成的作用。
b)Dynamic Point Selection:兩個基地台準備一樣的信號 但同時只會有一個基地台傳送信號。

17. Benefits of LTE-A compared with LTE
LTE-A與LTE的比較
載波能加總
更多的天線
更廣泛的涵蓋範圍
更容易管理

18. Reference
LTE to LTE-Advanced: What You Need to Know Right Now,
LTE-Advanced,