單元7 LTE與WiFi的負載分享排程演算法 (Load Scheduling)

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1 單元7 LTE與WiFi的負載分享排程演算法 (Load Scheduling)
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 「小基站與WiFi之異質性網路存取」課程模組 單元7 LTE與WiFi的負載分享排程演算法 (Load Scheduling) 助理教授：吳俊興 助教：王瑞元 國立高雄大學 資訊工程學系

2 Outline Overview LWIP and Wi-Fi Boost Flow Control
LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN 在OAI平台的LWA網路上使用UDP隧道實作影音 串流的雙介面傳送機制 Summary

3 Overview LTE macro-cells can provide high speed mobile data
But they can’t fulfill the increased subscribers’ demands in high density places Heterogeneous networks (HetNet) incorporate the coexistence of low power nodes along with a macro base station to improve coverage in high demand areas Seem to be a promise low cost solution from operators' point of view The HetNet variations are categorized into a single RAT (Radio Access Technology), multi-tier network, and a multi RAT multi-tier network The possible single RAT scenarios are : micro-cell, pico-cell, femto-cell or fixed relays (small cell) For the multi RAT scenario, the possible network components are: Wi-Fi offload, mobile hotspots and virtual carrier

4 Three Main Levels of Integration between Wi-Fi Networks and Cellular Networks

5 Conventional Wi-Fi Offloading Algorithms
Network access selection or offloading decisions, are made based on different parameters with different objectives as well, such as boosting the capacity or user QoS Two conventional algorithms Wi-Fi First algorithm (WF): Wi-Fi if coverage, which considers the SNR value to trigger the offloading decision to Wi-Fi Fixed SNR Threshold: based on choosing the best SNRmin for WLAN APs

6 Enhanced Offloading Algorithms
Best- Server algorithm Happens if SINR perceived by the user is greater than a certain threshold; otherwise he will connect to an LTE network Physical Data Rate Based algorithm (PDR) purely based on the PDR provided by different available RATs Compare the PDR for Wi-Fi and LTE, and chooses the highest value a user can get SMART algorithm Trigger the offloading based on the minimum data rate perceived by the user as long his experienced SINR exceeds the threshold

7 Effective Capacity Wi-Fi Offloading Algorithms

8 Case Studies LWIP and Wi-Fi Boost Flow Control
A new feature of Wi-Fi Boost, its radio link management, which allows to smartly steer the downlink traffic between both LTE and Wi-Fi upon congestion detection LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation Virtual WLAN Scheduler (VWS) which employs traffic steering scheme Five different bearer selection schemes have also been proposed which provide efficient steering by smartly choosing a bearer to route some data onto Wi-Fi

9 Case Studies (Cont.) A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN F-LBT jointly considers the total system throughput and the fairness between LTE-U and WLAN, and then allocates an appropriate idle period for WLAN 在OAI平台的LWA網路上使用UDP隧道實作影音 串流的雙介面傳送機制 (中山大學) 實作兩種雙介面傳送的技術，並且使用影音串流的資 料來傳輸，其中第一種是以串流為基礎，我們是將整 條串流經由 LTE 介面或 Wi-Fi 介面傳送，第二種是 以支流為基礎，我們是將一條串流分成 LTE 及 Wi-Fi 兩條支流，並且將兩條支流分別經由 LTE 及 Wi-Fi 介面傳送

10 Outline Overview LWIP and Wi-Fi Boost Flow Control
LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN 在OAI平台的LWA網路上使用UDP隧道實作影音串 流的雙介面傳送機制 Summary References

11 LWIP and Wi-Fi Boost Flow Control
Introduction and Background Data explosion 5G New Radio Access Technologies : Wi-Fi Aggregation Solutions LWIP(LTE WLAN Radio Level Integration with IPsec Tunnel)) Wi-Fi Boost : Advantages Architecture Compare with LWIP Algorithm Simulation & Result Conclusion

12 Introduction and Background
The Mobile Network in 2016 Global mobile data traffic grew 63 percent Mobile data traffic has grown 18-fold over the past 5 years Fourth-generation (4G) traffic accounted for 69% of mobile traffic Mobile offload exceeded cellular traffic by a significant margin Sixty percent of total mobile data traffic was offloaded onto the fixed network through Wi-Fi or femtocell 10.7 exabytes each month (1 EB = 1 billion GB) Almost half a billion (429 million) mobile devices and connections were added

13 CISCO Forecast Source :

14 5G Standardization Enhanced Mobile Broadband
Massive Machine Type Communications Ultra-Reliable Low-Latency Communications 5G的重要進度規劃為最快2018年制定規格，2020年商轉，因此電信業者多將於2019年前進行5G試運轉 5G接取技術、NFV/SDN技術、IoT服務平台、大數據分析、雲端運算、AR/VR相關影音等技術研發 Source : 3GPP TR v ( )

15 New Radio Access Technologies Wi-Fi Aggregation Solutions
從4G邁向5G時代，小型基地台(Small Cell)可以幫助運營商布建超密集網路，以滿足越來越高的頻寬速度及用戶體驗需求，並提供物聯網應用所需的綿密覆蓋。針對多樣化應用及場景，部署不同網路架構及功能需求的小型基地台，加上QoS/QoE還有行動邊緣計算等機制，能夠做到更深度的最佳化 行動通訊技術與Wi-Fi技術的搭配融合，將會成為打造完整網路通訊解決方案的關鍵所在，而以高通產品發展藍圖來看，Wi-Fi與行動通訊技術融合並存將是最大的重點，特別是在不同環境條件與應用需求下，能夠讓數據流量透過最具效率的網路進行傳輸，這將會是非常重要的發展關鍵。 Source :

16 LWIP(LTE WLAN Radio Level Integration with IPsec Tunnel)
Network Layer, Internet protocol Encrypt the original packet Add a new set of IP addresses The connection between the eNB and the UE is transmitted by the IPsec tunnel LWIP-SeGW LWIP技術毋須既有無線區域網路(WLAN)架構的改動，藉由使用者裝置(UE)透過WLAN建立IPSec通道至LTE eNB上的安全閘道器(Security Gateway)即可實現LTE與WLAN的聚合。 以訊號品質為標準 Source : 3GPP TS v ( )

17 Wi-Fi Boost : Advantages
Wi-Fi Boost uses LTE access for UL and frees up the enterprise’s existing Wi-Fi network for DL The solution works without any hardware or software upgrade on Wi-Fi infrastructure, and only requires a software upgrade on LTE eNBs and UEs Local access allows the UE to choose either LTE or Wi-Fi for UL applications anchored in the enterprise core that UEs can seamlessly and simultaneously draw on the strengths of both networks.

18 Architectures Commonalities
Both Wi-Fi Boost and LWIP R13 use as DL anchor the LTE eNB, and utilize IP layer as the split/aggregation point Both technologies are able to take advantage of the DL and UL split concept i.e. UL on LTE and DL on Wi-Fi An IPsec tunnel is used to transmit DL traffic from the LTE eNB to the UE through the Wi-Fi AP in a secure manner

19 Architectures Differences
Wi-Fi Boost uses over the top proprietary signaling to establish the IPsec tunnel, which only requires a software upgrade on LTE eNBs The Wi-Fi Boost solution allows for a more powerful radio link management, at the expense of the software upgrades required at the UE side in order to realize the necessary cooperation/feedback IP re-ordering and duplicate discard at the UE is another distinctive feature that can be made available in Wi-Fi Boost

20 Architectures

21 Wi-Fi Boost compare with LWIP
Way of IPsec tunnel set up The flow control/traffic steering capabilities Link switch Wi-Fi Boost Over the top proprietary signaling (RCM, UCM) Allow congestion detection, software upgrades of UE side IP re-ordering and duplicate discard at the UE LWIP R13 Layer radio resource control (RRC) signaling Report RSSI measurements on neighboring Wi-Fi APs to the LTE eNB Strength of the serving path is weak traffic steering only occurs when the strength of the serving path is weak when the strength of the serving path is weak, re-ordering and duplicate discard are not major issues. IP packets arrive at the UE simultaneously via different paths RRC連接無線資源的分配、重新配置和釋放

22 Radio Link Management – Initial Phase
Upon connection request, the LTE eNB will estimate which is the most suitable path for the given UE RAN connection manager (RCM) i) Fraction of probes lost, 𝑝𝑟𝑜𝑏𝑒𝐿𝑜𝑠𝑡 𝑢 ii) Average probe delay, 𝑝𝑟𝑜𝑏𝑒𝐷𝑒𝑙𝑎𝑦 𝑢 iii) Average probe throughput, 𝑝𝑟𝑜𝑏𝑒𝑅𝑎𝑡𝑒 𝑢 The fraction of probes lost is lower than a threshold, 𝑝𝑟𝑜𝑏𝑒𝐿𝑜𝑠𝑡 𝑢 < 𝑝𝑟𝑜𝑏𝑒𝐿𝑜𝑠𝑡 𝑚𝑎𝑥,𝑢 The average probe delay is shorter than a threshold, 𝑝𝑟𝑜𝑏𝑒𝐷𝑒𝑙𝑎𝑦 𝑢 < 𝑝𝑟𝑜𝑏𝑒𝐷𝑒𝑙𝑎𝑦 𝑚𝑎𝑥,𝑢 The average probe rate is higher than a threshold, 𝑝𝑟𝑜𝑏𝑒𝑅𝑎𝑡𝑒 𝑢 > 𝑝𝑟𝑜𝑏𝑒𝑅𝑎𝑡𝑒 𝑚𝑖𝑛,𝑢

23 Radio Link Management – Data Phase
Stall detection If 𝑥 𝑠𝑡𝑎𝑙𝑙 consecutive active probe ACKs are missing The RCM switches the UE over the LTE path Inactivity detection If the number of bits transmitted in between two probe ACKs is smaller than a threshold, 𝑈 𝑎𝑣𝑔,𝑢 < 𝑈 𝑚𝑖𝑛,𝑢 , meaning that the UE generates a small amount of traffic, the RCM switches the UE over the LTE path and the UE may decide to switch to Wi-Fi only mode to save resources Congestion detection If the filtered average UE throughput is smaller than a threshold, 𝑈 𝑎𝑣𝑔,𝑢 < 𝑇𝑃𝐻 𝑚𝑖𝑛,𝑢 , the RCM switches the UE over the LTE path

24 Flow Control Algorithm

25 Simulation & Result – Throughput CDF
The UE throughput cumulative distribution function (CDF) for the case where there are 4 UEs in the enterprise The LTE only case provides a median throughput of Mbps/UE, while the Wi-Fi only case provides a larger median throughput of Mbps/UE The WiFi only case benefits from more cells LWIP R13 and Wi-Fi Boost have a substantial gain over the Wi-Fi only case of around 2x The offloading of UL traffic from the unlicensed to the licensed band and the resulting collision-free usage of the unlicensed spectrum for DL (the so-called Boost effect) Comparison to that of LTE due to the inefficient sharing of resources between nodes and the contention/collision issues in the former

26 UE Throughput CDF

27 Simulation & Result – Throughput Distribution
The UE throughput distribution for the case where there are 32 UEs in the enterprise The even larger traffic load, and the resulting larger contention and congestion The gap between the performance of the LTE only and Wi-Fi only cases reduces further How CSMA/CA becomes more and more inefficient as the traffic load increases The larger congestion, the performance gain of LWIP R13 and Wi- Fi Boost with respect to the Wi-Fi only case is again larger LWIP R13 and WiFi Boost can enhance network performance up to 5x and 6x over LTE only, and 4x and 5x over Wi-Fi only networks Fig. 6 shows the system throughput (sum throughput of all cells) distribution for the case where there are 32 UEs in the enterprise

28 UE and System Throughputs

29 Conclusion Simulation performance Machine learning techniques
Up to 5x and 6x over LTE-only 4x and 5x over Wi-Fi only networks Further enhance over LWIP R13 up to 19 % Machine learning techniques Optimize the algorithm parameters Suggests to provide UE estimations to the LTE eNB on short-term throughput to detect congestion Enhance LWIP R13 UE feedback in future LTE releases

30 Outline Overview LWIP and Wi-Fi Boost Flow Control
LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN 在OAI平台的LWA網路上使用UDP隧道實作影音串 流的雙介面傳送機制 Summary References

31 LWIR : LTE-WLAN Integration at RLC Layer
Background and Motivation 5G Standard Feature Unlicensed band 3GPP LTE-H (Heterogeneous) technology Proposed Work LWIR Architecture VWS : One-Sized windowing technique VWS : Bearer/User Selection Schemes VWS : Feedback mechanism Simulation Setup and Performance Result Conclusion and Future Work

32 Background and Motivation
Cisco Visual Networking Index: Global Mobile Data Traffic Forecast Update, 2016–2021 Global mobile data traffic grew 63 percent in 2016 Mobile data traffic has grown 18-fold over the past 5 years Fourth-generation (4G) traffic accounted for 69% of mobile traffic in 2016 VNI=視覺網絡指數,複合成長率=CAGR 到2021年，思科預測移動數據流量將達到以下幾個里程碑： – 人均擁有1.5台移動設備。包括M2M模塊在內，總計近120億台移動聯網設備（2016年為80億台，人均1.1台）。 – 行動網絡聯接速度將增長3倍，從2016年的6.8 Mbps增長至2021年的20.4 Mbps。 – 機器對機器（M2M）聯接將佔移動聯接總量的29%（33億）—相比2016年的5%（7.8億），增長顯著。隨著全球物聯網（IoT）應用日益受到消費者和商業環境的青睞，M2M將成為增長最快的移動聯接類別。 – 智能手機（包括平板手機）總數量將佔全球設備和聯接總量的50%以上（62億）—相比2016年的36億有大幅增長。 移動應用的爆炸式增長和移動聯接在用戶終端的廣泛採用，正在推動4G急速增長，很快將帶動5G的增長。思科和其他行業專家預測，2020年5G基礎設施將開始大規模部署。移動電信運營商希望通過5G網絡提供顛覆式的速度、極低延遲和動態配置能力，以滿足日益增長的用戶需求，並更好地迎合跨移動、住宅和商業市場的全新服務趨勢 Global Mobile Devices and Connections Growth Global Mobile Traffic Growth by Device Type

33 5G Standard Feature High data rate and capacity
Low-Latency and Ultra-Reliable High energy efficiency Support IoT device New Radio Access Technology Massive MIMO Use more Spectrum : 10GHz ~ 100GHz Multi-cell Connectivity Wider bandwidth per carrier ”5G” 第五代行動通訊網路進行的研究指出，到了 2020 年，業界將可實現“事事處處永遠連接”的願景 ITU 定義的 4G 具有 1 Gbps 的單用戶資料速率。5G 的目標不是提高此速率，而是打造一個能夠提供此速率的高容量網路，以支援更大的用戶社群 提高網路容量有賴於 3 個因素：更多的頻譜、更好的調變效率，以及細胞體積逐漸縮小所帶來的頻率重複利用率 部署大量的小細胞，並透過高階 MIMO 增進其容量 多輸入輸出（Massive MIMO）技術 使用更多頻段︰10-100GHz 多站臺聯合傳輸（Multi-cell Connectivity） 更寬的載波（Wider bandwidth per carrier）

34 Unlicensed Band The wireless spectrum is limited
Increase the capacity of the cellular system LTE-U : 5GHz LTE-H : 2.4GHz, 5GHz(Wi-Fi) LWA, LWIP 無線頻譜是有限的。從長遠來看，這意味著只有那些非用行動裝置不可的應用，才能使用無線連接。其他服務則須盡可能地透過固網（光纖網路）來傳遞。我們已經看到在Internet上提供電視和廣播服務的蓬勃發展，其多元內容是地面或衛星廣播遠遠無法比擬的。而在行動網路中，今天的WiFi節點將成為未來的常態，以便增加蜂巢系統的容量，並為手機用戶提供最優質的服務 頻譜無法再增加的情況下，努力滿足長期需求。釋放出目前用於其他系統的頻段將成為第一優先考量。 開放公眾使用的頻譜用來擴充LTE的傳輸頻寬, 目前, 有以下兩種方法: LTE-U, LTE-H LTE-U是在ISM band上直接傳輸LTE的訊號, 並設計一種特有的頻譜共享機制, 和Wi-Fi一起競爭5GHz的通訊頻帶, 所收到的兩個不同頻帶訊號在手機上在合成為一個訊號, 雖然, LTE宣稱其設計的機制能比Wi-Fi更有效率, 但也面臨Wi-Fi陣營的抵制與挑戰, 因此, 3gpp只好重新設計另一個方案, 使用Wi-Fi的無線接取技術, 來化解Wi-Fi陣營的阻力, 這個方案稱為LTE-H, 也就是今天要討論的LTE Wi-Fi Link Aggregation (LWA). 如果無線接取也使用Wi-Fi的技術, 那麼, LWA和現有手機上同時有Wi-Fi和LTE網路的架構有甚麼不同呢?

35 3GPP LTE-H Technology LWA, LWIP LWIR
根據表格, 我們可以看到LWA和LWIP都是由eNB開始, 同時支援WiFi網路的訊號量測, 用以決定mobility set, 而LWA提供了和3gpp更緊密的整合, 包括對於同一個資料流的封包匯流, flow control機制, 以及快速認證機制, 但對WiFi網路架構有較多的修改, 至於LWIP則可以和既有WiFi網路結合, 直接提供上行和下行傳輸, 但是由於缺乏和LTE的協調機制, 在傳輸效能上應該較LWA差, 在LWA中, eNB和WT是在Layer 2溝通, LWIP則透過Layer 3溝通 若是WT為WiFi AP, LWA不需要額外裝置, 但是, WiFi AP必須修改 對於UE而言, 來自WiFi封包也屬於不同層, 在LWA中屬於Layer 2, LWIP中屬於Layer 3, 這也導致LWIP中的WiFi封包和LTE封包, 分屬不同服務, LWIP的架構中, 封包經由兩次轉傳 (UE-SeGW, SeGW-eNB), 效率較低 但在LWA架構中, 則須對原本802.11的架構的AP和UE都作出修改 Switched bearer – a bearer level offloading scheme in which a bearer is completely offloaded from LTE to Wi-Fi by PDCP layer(完全卸載到wifi) Split bearer – on the other hand some packets/flows of the bearer are put into the Wi-Fi by the PDCP layer(部分卸載到wifi) LWA, LWIP LWIR Reduces out-of-order delivery at the UE side When to switch between the radios How much data to route/steer through Wi-Fi

36 Variation in Congestion Window Size in LTE and LWA
Traffic control is mainly by size of Sliding Window (window size) to adjust If the receiver is too busy to handle the packet, the windows will become smaller 沒有好的流量控制，反而比只有LTE的時候還要延遲 結果，分組可能在UE側達到無序。 這再次增加端到端延遲，因為無序分組現在必須在PDCP層等待重新排序。 進行實驗以了解每個用戶從遠程主機下載大文件的30個用戶的完整加載單元中的此效果 所有流量都通過LTE網絡發送，而無需任何聚合，而在第二種情況下，通過應用LWA在LTE和WiFi接口之間平等（50:50）的流量轉移 可以看出，LWA中的擁塞窗口頻繁下降，其大小低於“僅LTE”場景中的擁塞窗口。 Wi-Fi和LTE中的分組必須分別在Wi-Fi MAC和RLC層隊列中等待，然後才能通過各個無線電接口發送。 由於LTE中的調度延遲和Wi-Fi中的競爭延遲，這些分組必須在這些隊列中等待不同的時間量。 結果，分組可能在UE側達到無序。 這再次增加端到端延遲，因為無序分組現在必須在PDCP層等待重新排序

37 Proposed Work LWIR Architecture Virtual WLAN Scheduler (VWS)
Traffic Steering Granularity How much data to steer? Bearer Selection for Wi-Fi Offloading Virtual WLAN Scheduler (VWS) One-sized windowing technique Bearer/User Selection Schemes Feedback mechanism 在RLC上創建可變大小的PDU的靈活性 限制卸載到Wi-Fi的數據量 選擇其中一個承載Wi-Fi卸載的緩衝區。 消除了RLC隊列中數據包的額外等待時間。 消除由Wi-Fi MAC隊列引起的延遲。 還提出一種反饋機制，通知通過Wi-F發送的通信量

38 One-sized Windowing Technique
Keeps a limit on the amount of data offloaded to Wi-Fi At most one packet kept in the Wi-Fi queue Never suffers from WiFi MAC queuing delay The VWS limits the size of RLC SDU to Maximum Transmission Unit (MTU) when it fetches from RLC buffer As LTE is a scheduled interface The achievable rate is deterministic Wi-Fi with random access based transmission gets increased throughput Increasing payload size of the packet The packet size (MTU) increases The number of transmitted packets decreases Reduces the total channel access delay – 可能會有很多設備然後爭奪wifi channrl > RLC PDU及時運送不被確保>無序的封包要在re-ordering緩衝器等待>確保可按順序運送>>>>>不必要的等待時間 – 最多一個數據包保存在Wi-Fi隊列中 LWIR with VWS works as follows: — LTE排程器從下行鏈路中選一個RLC緩衝器中取出一些字節。 — 除此之外，具有bearer選擇方案的VWS從一個緩衝區中取出一些字節，並打開Wi-Fi通道。 該封包（RLC SDU）被添加到Wi-Fi MAC佇列。 只有當Wi-Fi通過Wi-Fi發送該封包時，即Wi-Fi MAC佇列變空，然後VWS從透過Wi-Fi進行卸載的bearer選擇方案決定在相同緩衝器或不同緩衝器中選擇一些更多的字節。 >>>1確保任何時刻最多一個封包在wifi mac佇列2封包決不會承受來自wifi mac佇列的延遲 – VWS限制RLC SDU的大小>>最大transmission unit – 基於隨機存取傳輸的Wi-Fi透過增加封包的有效載荷大小來提高吞吐量 從而導致整體信道利用率的改善。

39 Bearer/User Selection Schemes
VWS picks the data by selecting a RLC buffer Based on the Bearer/User selection scheme Channel Quality Indicator (CQI) Min CQI First Interference region or at the edge of the cell Max CQI First Nearby the LWIR node receive better signal strength from both the radios Max RLC Buffer First Having highest amount of data in its RLC buffer Ensures maximum steering onto Wi-Fi Max RLC Buffer with Min CQI Sufficient amount of data in their RLC buffers Other user who has the least CQI is selected for steering onto Wi-Fi Max RLC Buffer with Max CQI  VWS選擇RLC緩衝器是基於bearer/user選擇架構 Bearer根據以下兩種挑選 – QoS requirement – Channel Quality Indication (CQI)渠道質量指標 — 1) Min CQI First(干擾區,邊緣用戶)因為LTE要發送更多的block與資源來傳送資料>>>效率低 — 2) Max CQI First(非常鄰近node之用戶)LTE就可以用來傳送中距離資料 — 3) Max RLC Buffer First(用戶在其RLC緩衝器中具有最高數據量，改善整理系統效能)因為沒有達到最大RLC緩衝資料量就傳送的話>>>wifi效率與使用率低<<<總是選擇其RLC緩衝區中具有最高數據的用戶。 — 4) Max RLC Buffer with Min CQI (1+3)優先:RLC緩衝器裡數據量足夠>最差CQI>3 (吞吐量將會高一些，因為我們也確保最大可能的數據一直被傳輸。) — 5) Max RLC Buffer with Max CQI (2+3)具有更好的CQI的用戶之數據的流量導引將提供更好的吞吐量，因為Wi-Fi的信號強度對於該用戶也會是好的。(吞吐量將會高一些，因為我們也確保最大可能的數據一直被傳輸。)

40 Feedback Mechanism Fair resource allocation
Conveys amount of data being steered onto the Wi- Fi network to the LTE scheduler In Proportional Fair scheduler, the user selection priority function is given by 公平的資源分配 – 將”導引到wi-fi網絡的數據量”傳送給LTE排程器 – x原本LTE要在某時間內要傳送的資料量, 以wifi傳送資料量y, 更新LTE要傳送的資料量=x-y – user selection priority function: P=Ta/Rb PF = Proportional fair 比例公平 T表示用戶在目前時段中可能達到的數據速率。 𝑅是歷史平均資料傳輸率，α和β是“公平”參數。 調度器還考慮在之前時間的期間內傳輸的數據量。 在這些時期內，數據已被傳輸到LTE和Wi-Fi鏈路中的哪一個無關緊要 因此，在邏輯上，對於LTE和Wi-Fi網絡都進行調度。 因此，我們稱之為虛擬WLAN調度器。

41 Simulation Setup LWIR architecture along with VWS functionalities in NS-3 LWIR node uses Wi-Fi Only in Downlink One Macro eNB and one LWA/LWIR/LWIP node in the simulation scenario 30 UEs : each UE one downlink flow Tested with TCP based flows Wi-Fi only in downlink 30 UEs, 每個用戶已經被設置一個bearer來運送data, the terms bearer and user are interchangeably. 為了檢查不同承載選擇方案的性能，本方案採用基於TCP的流量進行測試，其中每個用戶在模擬實驗期間從遠程主機下載大文件 為了在LWA / LWIR / LWIP單元中產生高交錯干擾，我們向Macro UE分別引入了每個3.25Mbps的五個下行鏈路UDP流（每個UE一個）作為Macro cell中的背景流量 我們比較了所提出的LWIR與LWA的性能。 – 在LWA中，通過LTE和Wi-Fi鏈路分配不同的百分比。 – LWA（30-70）意味著70％的流量被引導到Wi-Fi網絡，而其餘的仍然在LTE

42 Performance Results Total throughputs of TCP flows for flow level traffic steering in LWIP and split bearer traffic steering with varying split ratios at packet granularity in LWA Flow level traffic steering in LWIP which offloads some flows completely onto Wi-Fi Flow level traffic steering has rare chance of out-of-order packet reception at UE High number of DUPACKS With increase in the value of PDCP packet re-ordering timer, number of DUPACKS decreases The main cause for less throughput in LWA is waiting delay in Wi-Fi queue Improper choice of split ratio As the packets are coming through two different radio links RLC layer re-ordering logic Percentage of triple DUPACKS is decreased Larger congestion window which leads to higher TCP throughputs

43 Performance Results 圖5, LWIP中flow級流量導引的TCP flow總吞吐量&LWA中變化比例split bearer流量導引以封包粒度 – LWIP: flow level traffic steering in LWIP which offloads some flows completely onto Wi-Fi. – LWIP: rare chance of out-of-order packet – LWA: split bearer (packet level) traffic steering, there are high number of out-of-order packet receptions at PDCP layer of UEs – LWA: re-ordering buffer -> packets that are delayed too much 如果在PDCP分組重新排序定時器到期之前沒有到達UE，則分配比例的不正確選擇被認為是丟失的 6. 因為UE處的這個TCP接收器產生高數量的DUPACKS，這對TCP發送器的擁塞窗口的增長有負面影響，從而導致與LWIP提供的TCP吞吐量相比較低的TCP吞吐量 隨著PDCP分組重新排序定時器的增加，LWA的DUPACKS數量減少，但是其吞吐量仍然低於LWIP提供的吞吐量。 LWA的較少吞吐量的主要原因是Wi-Fi隊列中的等待延遲。 7 Min CQI First scheme具有高干擾性的用戶將由Wi-Fi提供服務。現在可以將LTE資源提供給高CQI用戶，並且有效地利用LTE資源 Max CQI First選擇具有良好CQI的用戶將其數據傳送到Wi-Fi網絡,隨著這些用戶更接近基站，Wi-Fi吞吐量增加。 小區邊緣用戶將由LTE服務,因為 LTE在比Wi-Fi更遠的地方表現更好 -LWIR但是由於RLC層重新排序邏輯，triple DUPACKS的百分比減小，如圖7所示 8.9. 在圖8和9中，我們可以清楚地看到，在最小CQI第一方案中，具有高干擾度的用戶將由Wi-Fi提供服務。現在可以將LTE資源提供給高CQI用戶，並且有效地利用LTE資源 在Max CQI中，首先選擇具有良好CQI的用戶將其數據發送到Wi-Fi網絡。隨著這些用戶更接近基站，Wi-Fi吞吐量增加。小區邊緣用戶將由LTE服務。 在具有最小CQI的最大RLC緩衝器和具有最大CQI的最大RLC緩衝器的最大RLC緩衝器中將遵循類似於最小CQI第一和最大CQI首先的相同行為。但是在這種方案中，吞吐量將會高一些，因為我們也確保最大可能的數據一直被傳輸。 10 最大RLC首先仍然執行與反饋機制一樣好，因為它不須知道CQI，並且它始終適用於具有最高數據的用戶發送 這真的有助於TCP流具有更大的擁塞窗口，這導致更高的TCP吞吐量

44 CDF for Different LWIR Bearer Selection Schemes
CDF for all the proposed bearer selection schemes Min CQI First and Max CQI First are selecting users for steering based on CQI Min CQI First is more fair as it is serving the cell edge users through Wi-Fi The Max RLC First is a load-aware scheme which always selects the user with the highest data in its RLC buffer All users are eligible to be selected for steering which makes it more fair The other two schemes consider CQI and load in their user selections and thus perform even better Max RLC First with feedback mechanism achieves better throughput as compared to scheduling CQI techniques and better fairness as compared to MAX RLC mechanism

45 CDF Result 累積分布函數，又叫分布函數，是機率密度函數的積分，能完整描述一個實隨機變量X的機率分布。一般以大寫「CDF」（Cumulative Distribution Function）表記。 1-CDF做積分 是期望值 看不出誰大誰小 看不出哪個有優勢 最小CQI第一和最大CQI首先是基於CQI選擇用於轉向的用戶。 最小CQI首先是通過Wi-Fi為小區邊緣用戶提供服務的公平性。 Max RLC First是負載-感知方案，其總是在其RLC緩衝器中選擇具有最高數據的用戶。 所有用戶都有資格選擇導引，這使得它更公平。 其他兩種方案考慮了CQI並加載其用戶選擇，從而執行得更好。 Max RLC First with feedback mechanism 比僅基於CQI技術更多吞吐量; 比MAX RLC mechanism更公平

46 Conclusions and Future Work
LWA Out-of-order packets problem LWIR with VWS Minimizes the delay generally caused in Wi-Fi network Maximum 85% throughput improvement over the LWA Only in the downlink Heavy interaction between the two MAC layers Only in the co-located scenarios Future work Uplink flows Non-collocated scenario 我們專注於TCP性能，並顯示LWA可能導致高級別的亂序數據包被接收 這會導致延遲，然後才能將數據包順序傳遞到應用程序 我們已經表明，使用虛擬WLAN調度程序提出的LWIR架構與LWA的數據包級別的流量轉向方法相比，吞吐量提高了85％。

47 Outline Overview LWIP and Wi-Fi Boost Flow Control
LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN 在OAI平台的LWA網路上使用UDP隧道實作影音串 流的雙介面傳送機制 Summary References

48 A Fair Listen-Before-Talk Algorithm
Background Introduction Coexistence Listen-Before-Talk (LBT) LBT Procedure Fair LBT (F-LBT) Algorithm

49 Background Recent report predicts that mobile data traffic will hit an annual run rate of Exabytes by 2019 A compound annual growth rate in the data traffic from 2014 to 2019 is 57 percent Many researchers pay attention to the interworking of different technologies Long term evolution (LTE) and wireless local area network (WLAN) to Maximize users’ quality of experience

50 Introduction LTE-U operation allows seamless data offloading by using a carrier aggregation technique Since LTE and WLAN are designed to operate in different bands, they do not have any coexistence mechanisms, which leads to significant performance degradation Since LTE does not sense for channel vacancy prior to transmissions The interference due to LTE transmissions severely affects the WLAN performance

51 Coexistence To prevent severe performance degradation
A simple coexistence scheme Uses a concept of blank subframe in the LTE frame structure Where the LTE-U access point (AP)1 does not transmit any data in the blank subframe Thus WLAN nodes can transmit data in the given blank subframe without any interference from LTE-U It is not clearly mentioned how to allocate blank subframes depending on the number of WLAN nodes A LTE uplink power control scheme where LTE devices decrease the uplink transmission power WLAN nodes can transmit data if WLAN nodes confirm the idle channel

52 Listen-Before-Talk (LBT)
By the ETSI recommendation for unlicensed bands LTE-U AP should employ a listen-before-talk (LBT) mechanism An equipment applies clear channel assessment (CCA) before using unlicensed bands Two LBT mechanisms: Frame-based LBT Load-based LBT

53 LBT Procedure Frame-based LBT Load-based LBT
An equipment checks the channel state during the CCA observation time The channel is idle The equipment transmits data during the channel occupancy time (COT) It should have an idle period which is more than 5% of COT The equipment shall not transmit on the channel during the next fixed frame period Load-based LBT The channel is idle, the equipment transmits data during COT The equipment shall perform an extended CCA check during a randomly extended time LTE operates with the fixed frame period The frame-based LBT is easy to be applied in LTE

54 Fair LBT (F-LBT) Algorithm
F-LBT determines an idle period in the frame- based LBT Jointly considering the fairness between LTE-U and WLAN, and the total system throughput Discrete time Markov chain (DTMC) F-LBT is based on the frame-based LBT A tactical LBT approach Easily implemented and deployed in real environments

55 System Model A network model where one LTE-U AP, NL LTE-U nodes, and NW WLAN nodes operate in the same unlicensed band Assume that all nodes are fully- connected and therefore there are no hidden nodes A frame in LTE consists of 10 subframes The duration of one subframe is 1 ms that is one transmission time interval (TTI) and thus the duration of one frame in LTE is 10 ms The LTE-U AP should have an idle period more than 5% of COT after it transmits data during COT

56 Analytical Model All nodes are connected, the channel can be used only by one system (i.e., WLAN or LTE-U) at the same time 𝑆 𝑁 𝐼 : The normalized total system throughput 𝑆 𝑁 𝐼 = 𝑆 𝑁 𝐼 𝑊 + 𝑆 𝑁 𝐼 𝐿 𝑁 𝐼 : The number of the idle sub frames 𝑆 𝑁 𝐼 𝑊 : The normalized WLAN throughput 𝑆 𝑁 𝐼 𝐿 : The normalized LTE-U throughput

57 DTMC Model Stochastic processes 𝑠 𝑡 : The backoff stage at time t
Stochastic processes b 𝑡 : The backoff counter at time t Idle state No data in the WLAN node’s buffer 𝑝 𝑓 : The probability that backoff counter freezes due to busy channel m : The maximum backoff state 𝑝 𝑎 : 1−𝑒𝑥𝑝 −𝜆 𝜎 , the probability that there is at least one data arriving during the unit slot time, 𝜎 𝜆 : The packet arrival rate 𝑝 𝐿 : 𝜆 𝜇 ,the probability that the buffer is not empty 𝜇 : The packet service rate 𝑊 𝑘 (0≤𝑘≤𝑚) : The maximum backoff counter in the kth backoff stage

58 Two-Dimensional DTMC for WLAN Node

59 Balance Equations By using the balance equations, we can obtain the closed form of the stationary probability of state (0,0) as: 𝑏 0,0 = 1 𝑊 1− (2𝑝 𝑐 ) 𝑚 1− 𝑝 𝑐 + ((2𝑝 𝑐 ) 𝑚 𝑊+1)(1− 2𝑝 𝑐 ) 2(1− 2𝑝 𝑐 )(1− 𝑝 𝑐 )(1− 𝑝 𝑓 ) + (1− 𝑝 𝐿 ) 𝑝 𝑎 The summation of stationary probabilities when the backoff counter is 0, is the transmission probability when the WLAN node and the LTE-U AP coexist 𝜏= 𝑗=0 𝑚 𝑏 𝑗,0 = 1 1− 𝑝 𝑐 𝑏 0,0 = 1 𝑊 1− (2𝑝 𝑐 ) 𝑚 1− 𝑝 𝑐 + ((2𝑝 𝑐 ) 𝑚 𝑊+1)(1− 2𝑝 𝑐 ) 2(1− 2𝑝 𝑐 ) (1− 𝑝 𝑓 ) + (1− 𝑝 𝐿 )(1− 𝑝 𝑐 ) 𝑝 𝑎

60 WLAN Equation 𝑝 𝑑 = [ 1− (1−𝜏) 𝑁 𝑊 𝑁 𝑇 + (1−𝜏) 𝑁 𝑊 𝑁 𝐼 ] 𝑁 𝑇
𝑝 𝑑 = [ 1− (1−𝜏) 𝑁 𝑊 𝑁 𝑇 + (1−𝜏) 𝑁 𝑊 𝑁 𝐼 ] 𝑁 𝑇 𝑆 𝑁 𝐼 𝑊 = 𝑃 𝑠 𝑃 𝑡𝑟 𝐸 𝑊 [𝑃] 1− 𝑃 𝑡𝑟 𝜎+ 𝑃 𝑡𝑟 𝑃 𝑠 𝑇 𝑠 + 𝑃 𝑡𝑟 (1− 𝑃 𝑠 ) 𝑇 𝑐 𝑃 𝑠 : The probability that a successful transmission occurs 𝑃 𝑡𝑟 : The probability that there is at least one transmitting WLAN node 𝐸 𝑊 [𝑃]: The average time for transmitting the payload in WLAN 𝑇 𝑠 : The average time for successful transmission 𝑇 𝑐 : The average time when the channel is sensed busy by a collision event

61 WLAN Nodes Do Not Transmit
𝑆 𝑁 𝐼 𝐿 = 𝐸 𝐿 𝑃 𝐻 𝐿 + 𝐸 𝐿 𝑃 +𝛿 𝑁 𝑇 − 𝑁 𝐼 𝑁 𝑇 (1−𝜏) 𝑁 𝑊 𝐸 𝐿 𝑃 : The average time for transmitting payload in LTE-U 𝐻 𝐿 : The transmission time for the packet header in LTE-U 𝛿: Propagation delay

62 Fair LBT Algorithm Step1: Estimation of the number of WLAN nodes and
Step 2: Determination of the number of idle sub frames

63 Evaluation Result - Nw Effect of Nw on S and F

64 Evaluation Result - a Effect of a on R

65 Conclusion F-LBT estimates the number of WLAN nodes and then determines the number of idle subframes Extend the proposed algorithm to reflect different channel qualities of each nodes Investigate time division duplexing (TDD) based LTE-U system Both uplink and downlink transmissions are conducted in the same band

66 Outline Overview LWIP and Wi-Fi Boost Flow Control
LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN 在OAI平台的LWA網路上使用UDP隧道實作影音串 流的雙介面傳送機制 Summary References

67 在OAI平台的LWA網路上使用UDP隧道實作影音串流的雙介面傳送機制
動機 論文使用機制 LWA-DM 串流資料 eNB 完成雙介面傳送的模組 UE 完成雙介面傳送的模組 eNB 的雙介面傳送 以串流為基礎的雙介面傳送 以串流為基礎的判斷流程 以支流為基礎的雙介面傳送 以支流為基礎的判斷流程

68 動機 目前市面上的UE 在單一時間只能使用一種介面來傳輸與接收 資料
如果單獨使用Wi-Fi 介面來傳輸影音串流，其它使用非執照頻 段的技術例如藍芽或感測器的訊號會產生干擾或雜訊 造成封包經由 Wi-Fi 傳輸時會產生位元錯誤 使得 UE播放的影片出現馬賽克 如果單獨使用 LTE 傳輸影音串流，eNB 可能會因為頻寬不足 UE播放的影片畫面會出現停格現象 LWA 是在數據聚合協定(Packet Data Convergence Protocol, PDCP)先將資料在 LTE 與 Wi-Fi 進行分流，並在 分流的資料加上 PDCP 序列號碼，使得 UE端可以將分流的資料進 行重組

69 論文使用機制 eNB 根據目前的負載來決定是否要啟動雙介面傳送 機制 雙介面傳送機制
串流為基礎 支流為基礎 都是在 eNB 的 PDCP 層進行 藉由 IP 住址來分辨不同串流 以支流為基礎的方法還需要使用PDCP序列號碼來將一條 串流分成兩條支流 eNB : PDCP 層會將不同串流或支流的封包分別經 由 LTE 及 Wi-Fi 傳送 UE : PDCP 層會使用兩個 Buffer 來重組封包

70 LWA-DM 結合 LTE 及 Wi-Fi 網路(LTE-WLAN Aggregation, LWA)的雙介面 (Dual-Mode)傳送機制 使用Wi-Fi (WLAN)來分擔 LTE 的負載，以提升 UE的 Throughput

71 串流資料 從Server 經過EPC 到eNB，eNB 會依照當前的 負載狀況判斷何時應該啟動或停止雙介面傳送
eNB 經由Ethernet 介面的EPC 從伺服器收到串 流資料的每個IP 封包後會送到Layer 2 的PDCP (Packet Data Convergence Protocol)層做處理 PDCP 層將封包分成要以Wi-Fi 傳送的封包以及不需 要以Wi-Fi 傳送的封包 不需要以Wi-Fi 傳送的封包會直接送往RLC 層做處理 要以Wi-Fi 傳送的封包則會送往新增加的Tunnel UDP 層及Tunnel IP 層做處理以建立UDP Tunnel 再傳到 Wi-Fi AP 的Ethernet 介面

72 串流資料 AP會將從Ethernet 介面收到的每個封包分別讀取 Tunnel IP 層的IP 住址及TunnelUDP 層的Port Number 以進行Network Address Translation (NAT) 轉換完成後AP 再透過UDP Tunnel 將每個封包傳送給UE 當UE 收到來自Wi-Fi 的封包後會讀取Tunnel IP 來 判斷封包是否來自UDP Tunnel 若是則繼續讀取TunnelUDP 層的Port Number 最後將封 包送往PDCP 層並解除UDP Tunnel 接著PDCP層會將來自LTE 與Wi-Fi 的封包根據序列 號碼(Sequence Number)進行重組 重組完成後PDCP 會將封包依序送往IP 層及UDP 層 抵達Video 的Decoder 進行解碼與Player 進行播放

73 eNB 完成雙介面傳送的模組

74 eNB 完成雙介面傳送的模組 紅色區塊是新增的模組,藍色區塊是修改 eNB 的模組,綠 色區塊則是 eNB 原始的模組
在 eNB原始的模組中，修改 PDCP 層來解析每個封包 的 IP Header 在 PDCP 層要將封包送往 RLC 層前 新增雙介面傳送模組來判斷雙介面傳送的方式 第一種是以串流為基礎(Stream-based)的雙介面傳送 第二種是以支流為基礎(Substream-based)的雙介面傳送 沒有以 Wi-Fi 傳送 的封包 依照 LTE 原始的程序將其送往 RLC 層處理 要以 Wi-Fi 傳送的封包 新增用來建立UDP Tunnel 的程序，建立 UDP Tunnel 的程序會 將封包加入 Tunnel IP 及 Tunnel UDP Header，接著透過 Socket 的方式將封包經由 Ethernet 介面送出並切斷封包送往 LTE 的 RLC 層

75 UE 完成雙介面傳送的模組

76 UE 完成雙介面傳送的模組 紅色區塊是新增的模組，藍色區塊是修改的 UE 模組， 而綠色區塊則是 UE原始的模組
新增一個專門處理 Wi-Fi 封包的 Thread 來與原有的 LTE Thread 並行處理封包， 對於使用UDP Tunnel 傳輸的 Wi-Fi 封包的處理如下所述， 在Wi-Fi Thread 中新增解除UDP Tunnel 的程序，當解除 UDP Tunnel 的程序收到來自 Wi-Fi 介面的封包時，由於需要經由 LTE 及 Wi-Fi 傳 送的封包的 PDCP 序列號碼來做為封包重組的判斷依據，在解除 UDP Tunnel 的程 序中解析封包的 PDCP Header 經由 LTE 介面傳送的封包，修改 LTE Thread 原始的 PDCP 層來抓取封包的 PDCP 序列號碼 在經由 LTE 及 Wi-Fi 傳送的封包其 PDCP 序列號碼都被記錄下 來後，在 LTE 及 Wi-Fi Thread 中新 增的封包重組模組便能以 序列號碼來重新排序封包並排除所有逾時的封包 當封包重新排序後，封包重組模組便會將經由 LTE 及 Wi-Fi 傳 送的封包依序送往 IP 層處理

77 eNB 的雙介面傳送 LWA-DM 設計兩種雙介面傳送的方法 設定 eNB 負載的上限當作啟動雙介面傳送的依據
第一種以串流為基礎(Stream-based) 的雙介面傳送方法 雙介面傳送模組將新產生的串流改由 Wi-Fi 來傳送 第二種以支流為基礎(Substream-based)的雙介面傳送方 法 雙介面傳送模組將雙介面傳送啟動前的最後一條串流 及雙介 面傳送啟動後產生的串流分成經由 LTE 及 Wi-Fi 傳送的兩條 支流 設定 eNB 負載的上限當作啟動雙介面傳送的依據 為了要在 eNB 上啟動雙介面傳送 每秒抓取 eNB 當前已使用的 RB 個數，並根 據已使用的 RB 個數在 eNB 最大可分配的 RB 總數中所佔的百分比做 為當前的 負載值 設定一個負載臨界值用來判斷是否啟動雙介面傳送

78 以串流為基礎的雙介面傳送

79 以串流為基礎的雙介面傳送 S表示 Server， UE 1 接收由 𝑆 1 透過LTE 傳送過來 的 Stream 1(黃線)，此時 eNB 的負載值仍未超 過設定的臨界值，因此不會啟動雙介面傳送 直到 UE 𝑘 也開始接收由 𝑆 𝑘 透過 LTE 傳送過來的 Stream k (綠線) 如果 eNB 連續統計一段時間的負載值都超過臨 界值就會啟動雙介面傳送 原有的 Stream 1 到 Stream k 封包並不會改由 Wi-Fi 傳送 在雙介面傳送開始之後，eNB 才會將新的 Streams (Stream k+1 到 Stream n)直接以 Wi-Fi 傳送

80 以串流為基礎的判斷流程

81 以串流為基礎的判斷流程 雙介面傳送啟動前，雙介面傳送模組會在 eNB 的 PDCP 層解析每個封包的IP Header 並記錄目的地 UE的 IP Address 當封包抵達 PDCP 層時，PDCP 層會記錄封包的目的地 IP( IP 𝑑𝑠𝑡 ) 接著雙介面傳送模組根據雙介面傳送啟動前紀錄的 UE IP 來比對 IP 𝑑𝑠𝑡 比對結果發現封包的目的地為雙介面傳送啟動前的 UE 雙介面傳送模組會將封包送往 RLC層 並以 LTE 傳送封包 比對結果發現封包的 IP 𝑑𝑠𝑡 不是雙介面傳送啟動前的UE 表示此封包的目的地是雙介面傳送啟動後新連線的 UE 雙介面傳送模組會將封包送往 Ethernet 介面並等待 eNB 的下 一個封包

82 以支流為基礎的雙介面傳送 雙介面傳送啟動前 雙介面傳送啟動後

83 以支流為基礎的雙介面傳送 雙介面傳送啟動前 雙介面傳送啟動後
以S表示 Server，首先 𝑈𝐸 1 接收由 𝑆 1 透過 LTE 傳輸的 Stream 1 (黃線)封包 eNB 的負載值仍未超過我們設定的臨界值，因此不會啟 動雙介面傳送 雙介面傳送啟動後 直到 𝑈𝐸 𝑘 也開始接收 𝑆 𝑘 透過LTE 傳輸的 Stream k (綠線) 後，由於負載值超過臨界值，因此 eNB 將會啟動雙介 面 傳送 在雙介面傳送啟動前產生的 Streams 中，除了 Stream k 之外的 Streams 都不會以雙介面傳送 當 eNB 收到 Stream k 到 Stream n 的封包時，這些 Streams 會被 eNB 各自分成 LTE 及 Wi-Fi 兩條支流 (Substreams)來傳送封包給UE

84 以支流為基礎的判斷流程

85 以支流為基礎的判斷流程 根據封包的目的地 IP ( IP 𝑑𝑠𝑡 )來判斷那些串流的封包要以 雙介面傳送 對於要以雙介面傳送的串流封包
雙介面傳送模組會將 PDCP 序列號碼在 0 到最大值之間分成數 段長度相同的序列號碼範圍 首先會以 Wi-Fi 傳送一段序列號碼範圍的封包 接著再以 LTE 傳送下一段序列號碼範圍的封包 交替使用 LTE 及 Wi-Fi 傳送封包的方式來達成將一條串流分成 LTE 及 Wi-Fi 兩條支流的效果 在PDCP層傳送封包前會記錄PDCP層替封包配置的 PDCP序列號碼( 𝑆𝑁 𝑝𝑘𝑡 ) 以 𝑆𝑁 𝑝𝑘𝑡 來判斷是否在Wi-Fi支流負責傳送的序列號碼範圍內 若封包要由 Wi-Fi 支流傳送，將封包送往 Ethernet 介面 若封包要由 LTE 支流傳送，雙介面傳送模組會將封包送往 RLC 層

86 結論 在以串流為基礎的雙介面傳送方法中 在以支流為基礎的雙介面傳送方法中
UE 除了會經由 LTE 介面接收資料, 同時還會經由 Wi-Fi 介面接收資料,所以 UE 在單位時間的吞吐量會 比沒有 使用 LWA-DM 的機制時更高 在以支流為基礎的雙介面傳送方法中 如果每 64 個封包切換支流,UE 在每 一秒的吞吐量都 會提升,如果每 1024 個封包才切換支流,UE 每隔 12 秒吞 吐量才會提升一次,但是每 64 個封包就切換支 流,eNB 的處理延遲會比每 1024 個封包才切換一次 支流所需的時間更久

87 Outline Overview LWIP and Wi-Fi Boost Flow Control
LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN 在OAI平台的LWA網路上使用UDP隧道實作影音串 流的雙介面傳送機制 Summary References

88 Summary LWIP and Wi-Fi Boost Flow Control
A Wi-Fi Boost flow control algorithm with congestion detection to make LTE and Wi-Fi integration more efficient Congestion detection mechanism is based on IP probing and can work with any Wi-Fi AP LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation A unique RLC layer integration architecture LWIR and a Virtual WLAN Scheduler containing a data steering scheme One-Sized A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN F-LBT estimates the number of WLAN nodes and then determines the number of idle subframes 在OAI平台的LWA網路上使用UDP隧道實作影音串流的雙介面傳送機 制 提升UE 在單位時間的吞吐量，並且卸除 eNB 的負載，針對以串流為基礎和 以支流為基礎的兩種雙介面傳送方法來實作

89 References T. Alruhaili, G. Aldabbagh, F. Bouabdallah, N. Dimitriou, & M. Win, Performance Evaluation for Wi-Fi Offloading Schemes in LTE Networks, International Journal of Computer and Information Sciences, Vol. 12, 2016, pp Lopez-Perez, D., Ling, J., Kim, B. H., Subramanian, V., Kanugovi, S., & Ding, M., LWIP and Wi-Fi Boost Flow Control, IEEE Wireless Communications and Networking Conference, 2017 Sharma, P., Brahmakshatriya, A., Pasca S, T. V., Tamma, B. R., & Franklin, A., LWIR: LTE-WLAN Integration at RLC Layer with Virtual WLAN Scheduler for Efficient Aggregation. Paper presented at the Global Communications Conference (GLOBECOM), 2016 Ko, H., Lee, J., & Pack, S., A Fair Listen-Before-Talk Algorithm for Coexistence of LTE-U and WLAN. IEEE Transactions on Vehicular Technology, 65(12), 2016 李俊德, 在OAI平台的LWA 網路上使用UDP隧道實作影音串流的雙介面傳送機制, 國立中山大學碩士論文, 2017