Today almost half the world's population does not have Internet access. This is particularly the case in rural and undeserved regions where providing Internet access infrastructure is challenging and expensive. To this end, we present demonstration of WhiteHaul [5], a low-cost hybrid cross-layer aggregation system for TV White Space (TVWS) based backhaul. WhiteHaul features a custom-designed frequency conversion substrate that efficiently handles multiple noncontiguous chunks of TVWS spectrum using multiple low-cost COTS 802.11n/ac cards but with a single antenna. At the software layer, WhiteHaul uses MPTCP as a link-level tunnel abstraction to efficiently aggregate multiple chunks of the TVWS spectrum via a novel uncoupled, cross-layer congestion control algorithm. This demo illustrates the unique features of the WhiteHaul system based on a prototype implementation employing a modified version of MPTCP Linux Kernel and a custom-designed conversion substrate. Using this prototype, we highlight the performance of the WhiteHaul system under various configurations and network conditions

Buneman, P

Kassem, MM

Kheirkhah, M

Marina, MK

English

UCL Discovery

WhiteHaul – white space spectrum aggregation system for backhaulCitation for published version:Kassem, M., Kheirkhah, M., Marina, M.K. and Buneman, P., 2020, September. WhiteHaul: white space spectrumaggregation system for backhaul. In Proceedings of the 26th Annual International Conference on Mobile Computingand Networking (pp. 1-3). https://doi.org/10.1145/3372224.3417319Link:Link to published version in ACM Digital LibraryDocument Version:Peer reviewed versionPublished In:Proceedings of the 26th Annual International Conference on Mobile Computing and Networking (MobiCom ‘20)Demo: WhiteHaul – White Space Spectrum AggregationSystem for BackhaulMohamed M. Kassem∗Cairo UniversityMorteza KheirkhahUniversity College LondonMahesh K. MarinaUniversity of EdinburghPeter BunemanUniversity of EdinburghABSTRACTToday almost half the world’s population does not have Internet ac-cess. This is particularly the case in rural and undeserved regionswhere providing Internet access infrastructure is challenging andexpensive. To this end, we present demonstration of WhiteHaul [5], alow-cost hybrid cross-layer aggregation system for TV White Space(TVWS) based backhaul. WhiteHaul features a custom-designed fre-quency conversion substrate that efficiently handles multiple non-contiguous chunks of TVWS spectrum using multiple low-cost COTS802.11n/ac cards but with a single antenna. At the software layer,WhiteHaul uses MPTCP as a link-level tunnel abstraction to efficientlyaggregate multiple chunks of the TVWS spectrum via a novel uncou-pled, cross-layer congestion control algorithm. This demo illustratesthe unique features of the WhiteHaul system based on a prototype im-plementation employing a modified version of MPTCP Linux Kerneland a custom-designed conversion substrate. Using this prototype,we highlight the performance of the WhiteHaul system under variousconfigurations and network conditions.KEYWORDSUniversal Internet access, Rural connectivity, Backhaul, TV whitespace spectrum, Spectrum aggregation, Multipath TCP1 INTRODUCTIONToday, almost half the world’s population is still unconnected to theInternet [3], and predictably a large fraction of it lives in rural and/orunderserved areas. In the past decade, there have been a series ofefforts to remedy this through community cellular networks, initiallyfocused on voice and SMS services [3, 13] and more recently onLTE based mobile broadband Internet service [6, 11] leveragingthe emergence of open-source software platforms. However, despitethese developments, the backhual infrastructure is still limited andcostly, and this remains a major roadblock [11, 12]. For example,common approaches for the backhaul connectivity rely on fiber, li-censed microwave or satellite solutions have high CAPEX or OPEXcosts [12].A viable approach to overcome this barrier is to exploit spectrumwhite spaces, notably the TV white space (TVWS) spectrum — the∗M.M. Kassem was with the School of Informatics, The University of Edinburgh whenthis work was done.Permission to make digital or hard copies of part or all of this work for personal orclassroom use is granted without fee provided that copies are not made or distributed forprofit or commercial advantage and that copies bear this notice and the full citation onthe first page. Copyrights for third-party components of this work must be honored. Forall other uses, contact the owner/author(s).MobiCom ’20, September 21–25, 2020, London, United Kingdom© 2020 Copyright held by the owner/author(s).ACM ISBN 978-1-4503-7085-1/20/09.https://doi.org/10.1145/3372224.3417319InternetWhiteHaul LinkControl ChannelData ChannelsMasterNodeSlaveNodeAccess NetworkFigure 1: High-level schematic of WhiteHaul system in an end-to-end application scenario.Traffic Management ModuleTraffic Scheduler(MPTCP)Slot AllocationManagerInterface Configuration ModuleSpectrumSensingGeolocationDatabase ManagerCoordination ModuleDataInterface 1DataInterface NControl Interfaceand GPS ReceiverTVWS Conversion SubstrateWhiteHaulSoftwareLayerWhiteHaulHardwareLayerFigure 2: WhiteHaul node architecture.portions of UHF TV bands unused by the incumbents. TVWS spec-trum is attractive for backhaul connectivity in rural and developingregions for multiple reasons: (1) the low cost aspect (no spectrumlicensing fees); (2) the ample spectrum availability in rural areas; and(3) the superior propagation characteristics of UHF TV spectrumcompared to other higher frequency bands in terms of both rangeand non-line-of-sight (NLoS) propagation in presence of foliage andobstructions [2, 4, 8]. Despite the promise of TVWS spectrum forbackhaul connectivity in rural regions, existing TVWS systems –both commercial solutions and research prototypes [1, 7, 9, 11] –fail to fully realize this promise as the throughput they can achieveis limited to a few tens of Mbps — insufficient for even a modestcommunity of network users.In this work, we propose to demonstrate WhiteHaul [5], the firstTVWS based spectrum aggregation system for backhaul that candeliver an order-of-magnitude higher throughput (nearly 600Mbps)than the state-of-the-art by addressing several significant challengesand constraints pertinent to the backhaul use case. First, individualTVWS channels are narrow (6/8MHz depending on the regulatoryregime). Second, available channels may not be contiguous, makingit imperative to aggregate multiple possibly non-contiguous TVWSspectrum chunks to realize high-speed TVWS backhaul connectivity.Third, TVWS spectrum exhibits a high degree of diversity in termsof chunk sizes, transmit power and interference levels. Fourth, costand ease of deployability concerns make a single antenna systemthe preferred option. Lastly, backhaul traffic exhibits high degree ofasymmetry and temporal fluctuations.MobiCom ’20, September 21–25, 2020, London, United Kingdom Mohamed M. Kassem, Morteza Kheirkhah, Mahesh K. Marina, and Peter Buneman 0 100 200 300 400 500 600 700 0  1  2  3  4  5  6  7Throughput (Mbps)MCS20+20+20MHz20+20+40MHz20+40+40MHz40+40+40MHz40+40+80MHz40+80+80MHz80+80+80MHz(a)0.1%42Mb/s1.1%70Mb/s3.3%84.5Mb/s5.4%205Mb/s6.9%105Mb/sPacket Loss (%)Capacity (Mb/s)0.1%42Mb/s1.1%70Mb/s3.3%84.5Mb/s5.4%205Mb/s6.9%105Mb/s 0 0.2 0.4 0.6 0.8 1(b)0.1%42Mb/s1.1%70Mb/s3.3%84.5Mb/s5.4%205Mb/s6.9%105Mb/sPacket Loss (%)Capacity (Mb/s)0.1%42Mb/s1.1%70Mb/s3.3%84.5Mb/s5.4%205Mb/s6.9%105Mb/s 0 0.2 0.4 0.6 0.8 1(c)Figure 3: (a): WhiteHaul aggregate TCP throughput in a three interface scenario; (b) aggregation efficiency comparison betweenWhiteHaul MPTCP and (c) uncoupled MPTCP with CUBIC, in different conditions (as a heatmap – red is best).In particular, the focus of this demo is on highlighting the uniquefeatures of the WhiteHaul system including: (i) the aggregation ofmultiple non-contiguous chunks of TVWS spectrum with a customdesigned frequency conversion substrate; and (ii) the novel use ofMPTCP as a link-level tunneling technique that enables efficient ag-gregation through a new cross-layer congestion control algorithm [5].2 WHITEHAUL OVERVIEWWhiteHaul is intended to realize point-to-point (PtP) TVWS basedbackhaul links, meaning a WhiteHaul node forms the endpointsof such a link. Fig. 1 shows a basic application scenario where aWhiteHaul link connects an access network (serving end-user devices)and the Internet. We do not make any assumptions on the nature ofthe access network, which could take several forms including a com-munity cellular network (e.g., [11]). As shown in Fig. 1, we adopta Master-Slave model in that one end of a WhiteHaul link actsas the Master Node and the other as the Slave Node with theformer responsible for link configuration decisions (e.g., spectrum touse for interfaces on both sides). The Master and Slave coordi-nate over an out-of-band control channel while carrying user trafficover multiple data channels that each operate on a separate TVWSspectrum chunk. Fig. 2 provides the schematic of the WhiteHaul nodearchitecture that consists of Hardware Layer and Software Layer.Hardware Layer. This is designed based on the multi-radio ar-chitecture principle to combine the multiple non-contiguous TVWSspectrum chunks. Specifically, the hardware layer is composed oftwo types of physical wireless interfaces used for both control anddata communication as well as the TVWS conversion substrate forthe data interfaces. For the data interfaces, we use multiple low-costCOTS 802.11n/ac Wi-Fi cards operating in 5GHz band and designthe conversion substrate to perform the frequency up/down conver-sion between available TVWS spectrum chunks and 5GHz Wi-Fichannels. These multiple Wi-Fi cards are combined together intoa single antenna to avoid higher towers, which steeply increase thecost and deployment complexity. For the control interface, we useLoRa [10], a low-power wide area network technology.Software Layer. This layer orchestrates the underlying interfacesto maximize the overall system performance. It is made up of threemodules: (i) the Coordination Module facilitates communicationbetween the Master and Slave nodes via the underlying LoRacontrol interface; (ii) the Interface Configuration Module configuresthe TVWS spectrum chunks and transmit power of data interfacesas decided by the Master node. These configurations are basedon the TVWS spectrum availability information obtained from thegeolocation database and local low-cost spectrum sensing from bothends of the WhiteHaul link; (iii) the Traffic Management Moduleperforms two functions. One, by the Slot Allocation Manager, isto adapt the time allocation between Master-Slave (forward)and Slave-Master (reverse) directions, every epoch, dependingon the effective capacity and traffic demand of forward and reverselinks. The Traffic Scheduler is responsible for the other function toefficiently schedule the traffic among the underlying data interfacesusing a modified variant of MPTCP, aided by signals from the SlotAllocation Manager (see [5] for more details).3 DEMONSTRATIONThe goal of this demonstration is twofold: (i) to demonstrate thecapabilities of WhiteHaul system and show its performance under dif-ferent configurations (e.g., using contiguous/non-contiguous TVWSspectrum chunks); (ii) to show how the new MPTCP cross-layercongestion control algorithm helps to achieve robust performanceunder various network conditions (e.g., packet losses).We use a testbed setup similar to Fig. 1 where it consists of fourIntel i7 machines (7567U processor at 3.5GHz, 8GB of RAM). Thefirst node represents the access network side and it acts as a clientin the local community network. Two other nodes represent bothWhiteHaul Slave and Master nodes, and the last node acts as alocal server that represents the Internet PoP. Both WhiteHaul Slaveand Master nodes run our modified MPTCP Linux Kernel imple-mentation, and is connected to a low-cost Pycom LoRa gateway,three Mikrotik 802.11ac Wi-Fi cards and the TVWS conversion sub-strate. The Wi-Fi cards and the conversion substrate are configuredby the Interface Configuration Module in the software layer (SeeFig. 2). We then use iperf to generate TCP traffic between the clientand the local server nodes. That traffic is carried over 3 contiguousTVWS spectrum chunks with a total size of 240 MHz. Fig. 3a showsthat WhiteHaul can provide maximum TCP throughput up to nearly600Mbps in that given setup.For the second part of the demonstration, we emulate the packetlosses using Linux Network Emulator (NetEm) and real-world linkloss values discussed in [5]. Figs. 3b, 3c display the results of WhiteHaulMPTCP compared to uncoupled MPTCP using CUBIC as heatmapsof efficiency, defined as the ratio of achieved throughput (in presenceof losses) for a given MPTCP algorithm to the maximum achievedthroughput (without losses). Overall WhiteHaul algorithm achievessuperior performance, by an order of magnitude, compared to CU-BIC, thanks to the periodic feedback from the underlying layers thathelps to keep track of optimal congestion window size, and allowsquick ramp up for the sending rate in case of random packet drops.Demo: WhiteHaul – White Space Spectrum Aggregation System for Backhaul MobiCom ’20, September 21–25, 2020, London, United KingdomREFERENCES[1] Carlson Wireless Technologies. https://www.carlsonwireless.com/.[2] Flores, A. B., Guerra, R. E., Knightly, E. W., Ecclesine, P., and Pandey,S. IEEE 802.11 af: A standard for TV white space spectrum sharing. IEEECommunications Magazine 51, 10 (2013), 92–100.[3] Heimerl, K., Hasan, S., Ali, K., Brewer, E., and Parikh, T. Local, Sustainable,Small-Scale Cellular Networks. In Proceedings of the Sixth International Con-ference on Information and Communication Technologies and Development: FullPapers-Volume 1 (2013), ACM, pp. 2–12.[4] Johnson, D. L., and Mikeka, C. Bridging Africa’s broadband divide. IEEESpectrum 53, 9 (2016), 42–56.[5] Kassem, M. M., Kheirkhah, M., Marina, M. K., and Buneman, P. Whitehaul:An efficient spectrum aggregation system for low-cost and high capacity backhaulover white spaces. In Proceedings of the 18th International Conference on MobileSystems, Applications, and Services (New York, NY, USA, 2020), MobiSys ’20,Association for Computing Machinery, p. 338–351.[6] Kassem, M. M., Marina, M. K., and Radunovic, B. DIY model for mobilenetwork deployment: A step towards 5G for all. In Proceedings of the 1st ACMSIGCAS Conference on Computing and Sustainable Societies (2018), pp. 1–5.[7] Khalil, M., Qadir, J., Onireti, O., Imran, M. A., and Younis, S. Feasibility,architecture and cost considerations of using TVWS for rural Internet access in5G. In 2017 20th Conference on Innovations in Clouds, Internet and Networks(ICIN) (2017), IEEE, pp. 23–30.[8] Kumar, A., Karandikar, A., Naik, G., Khaturia, M., Saha, S., Arora, M.,and Singh, J. Toward enabling broadband for a billion plus population with TVwhite spaces. IEEE Communications Magazine 54, 7 (2016), 28–34.[9] Kumbhkar, R., Islam, M. N., Mandayam, N. B., and Seskar, I. Rate optimaldesign of a wireless backhaul network using TV white space. In 2015 7th Interna-tional Conference on Communication Systems and Networks (COMSNETS) (2015),IEEE, pp. 1–7.[10] Raza, U., Kulkarni, P., and Sooriyabandara, M. Low Power Wide AreaNetworks: An overview. IEEE Communications Surveys & Tutorials 19, 2 (2017),855–873.[11] Sevilla, S., Johnson, M., Kosakanchit, P., Liang, J., and Heimerl, K. Experi-ences: Design, Implementation, and Deployment of CoLTE, a Community LTESolution. In The 25th Annual International Conference on Mobile Computing andNetworking (2019), ACM, p. 45.[12] Yaacoub, E., and Alouini, M. Connecting the Remaining 4 Billions: A Surveyon Rural Connectivity. CoRR abs/1906.11541 (2019).[13] Zheleva, M., Paul, A., Johnson, D. L., and Belding, E. Kwiizya: Local CellularNetwork Services in Remote Areas. In Proceedings of ACM MobiSys (2013),ACM, pp. 417–430.

WhiteHaul: white space spectrum aggregation system for backhaul

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WhiteHaul: white space spectrum aggregation system for backhaul

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