Unlicensed LTE WHITE paper

Transcription

1 Unlicensed LTE WHITE paper

2 Table of Contents Abstract Executive Summary Introduction LTE Unlicensed LTE vs. Wi-Fi a comparison Co-Channel Co-existence One step ahead with LWA Market Trends, offerings and challenges Abbreviations References

3 Abstract As the data demand continues to explode, problems of frequent call drops, poor indoor coverage, and low throughput spoils the user experience for the ubiquitous connectivity service. Spectrum Crunch - This situation is due to lack of sufficient radio frequencies to cater to the growing number of mobile user base and proliferation of smart phones in the mass. Hence, telecom service providers are looking for better radio/modem technology, better spectral efficiency, and more radio spectrum. In this context, the relevance and value that unlicensed spectrum is going to add to the telecom network cannot be underestimated. Using LTE (long-term evolution) a spectrally efficient cellular technology over the unlicensed spectrum is a potential solution to this grave problem! LTE unlicensed is an emerging topic in research, standardization, and deployment of 3GPP (3rd Generation Partnership Project) networks. It propagates the benefits of LTE and LTE-A to unlicensed spectrum, and enables mobile operators to offload mobile data to unlicensed frequencies more effectively and efficiently. Mobile consumers experience better cellular coverage and higher download speeds. With spectrum being a scarce resource, LTE-U has emerged as a profitable option for operators to increase capacity without any additional spectrum licensing cost. Big-Data will need bigger and fatter pipes to flow, and LTE-Unlicensed would play an important role in achieving that. It is also important to discuss the challenges for co-existence and available solutions, to achieve the harmony and ensure fair access to the spectrum users. LTE-U forum and Wi-Fi forum have to come together and join hands to make this possible. After briefing on ISM (Industrial, Scientific, and Medical) bands, this paper describes two flavors of LTE unlicensed access, LTE-U and LAA (Licensed Assisted Access). Depending on the regulation restrictions in different geographies, either LTE-U or LAA will be deployed. Comparing LTE and Wi-Fi over a few major aspects, it outlines the problems of co-existence, and discusses various medium access mechanisms to ensure harmony. An alternate solution called LWA (LTE Wi-Fi Aggregation) has also been briefly introduced. Later, the paper provides insight on market trends, market offerings, and the challenges existing for market players in the battlefield of unlicensed LTE. Executive Summary With the advancements in telecommunication industry, the provision of ubiquitous connectivity to the users is no more a daydream. The massive shift from wireline traffic to wireless traffic in the past decade shows that mobile traffic is gaining increasing attention. However, this gain has the associated problem of Radio Spectrum Crunch to cater to the exponential growth of user data demands. LTE Unlicensed is a potential technology, which makes use of LTE protocol over the unlicensed spectrum. The ISM (Industrial, Scientific and Medical) band, mainly considered for this solution is 5GHz unlicensed band, as the 2.4GHz ISM band is already congested. Cordless Phones, Bluetooth, ZigBee, NFC Devices take advantage of unlicensed spectrum for short-range communication. The WLAN protocol Wi-Fi also operates in unlicensed bands to provide superior indoor-coverage. With LTE Unlicensed, the ISM band will have LTE as an additional contender sharing the same resource-pie. As LTE protocol is designed for licensed band, the channel access mechanism here is synchronous, whereas Wi-Fi is asynchronous in nature. The major difference in channel access mechanism of both the technologies leads to serious problems like Interference and Starvation when they co-exist. Wi-Fi, being the major user of unlicensed band, the supporters of this upcoming technology - LTE Unlicensed are facing strong oppositions from the Wi-Fi Alliance members like Apple, Google, Comcast, and Microsoft.

4 This paper describes primarily two flavors of Unlicensed LTE technology 1. LTE-U (LTE-Unlicensed) and 2. LAA (Licensed Assisted Access). Implementation for both of these requires an anchor in licensed spectrum. LTE-U, is based on 3GPP Release 10 (LTE-Advanced) feature named Carrier Aggregation, whose standards are already in place. Regions like USA, China, and Korea will see early deployments of LTE-U. However, a much global solution, the LAA based on Release 13 specifications, mandates the implementation of LBT (Listen Before Talk) technique, will be commercialized later due to ongoing standardization. When LBT is enabled, each device or access point would scan the channel to detect any activity on this channel and transmit only when it finds the medium unused. Thus it ensures fair co-existence of other technologies and devices operating in the same spectrum. LBT being a global approach, this would be compliant with regulatory requirements of most countries like Europe and Japan. The reason behind adopting Unlicensed LTE is not to overpower the reign of Wi-Fi, but to enhance spectral efficiency and capacity of 5GHz band by co-existing harmoniously and ensuring fair medium access. There is no doubt that these LTE and Wi-Fi technologies with their rich and complementing features will continue to converge with the goals of giving users Anytime & Anywhere connectivity and required bandwidth. Users do not care which underlying technology is being used to cater to their services, as long as it is fast, affordable, and reliable. As these two (licensed and unlicensed) worlds cater to some conflicts of interest, understanding the differences between discussed approaches is important. This helps in realizing that there is no right or wrong, just difference of choices. Currently, the future looks bright for carrier grade Wi-Fi technology and LTE Small Cells. LTE-U, LAA, LWA are different approaches for converging the best of both worlds together and probably other options will emerge as well. Like everything, the market is the only Ultimatum! It will decide what works best and when.

5 Introduction Motivation The massive shift from wireline traffic to wireless traffic in the past decade shows that the mobile traffic is gaining increasing attention. The use of wireless data services gives consumers the freedom of mobility. Today wireless traffic accounts for more than half of the IP traffic and most of them is not cellular, but Wi-Fi, according to Cisco s VNI data. Global IP traffic Wireless traffic 59% 41% Wireless traffic 75% 24% 61% 55% 4% 15% Cellular Wi-Fi Fixed IP Fig. 1: Wireless Traffic Scene, Source: Cisco VNI Traditional Cellular providers find it challenging to provide good indoor-coverage. Hence, Wi-Fi dominates in most of the residential and enterprise setups for indoor data services. People spend 80-90% of their time indoors. Network analytics shows that the majority of mobile data usage, close to 80%, is indoor and not truly mobile. Hence, there is a growing pressure on mobile operators to provide those users fast and seamless connectivity with the existing problem of Spectrum Crunch. At the same time, it can be seen as a great business opportunity for the MNOs to increase their indoor customer count with enhanced indoor coverage. Fixed line operators can get a better level of management layer from the cellular operators and can provide a good amount of bandwidth even to users who are away from the amplifiers. The 3GPP LTE technology is a 4G cellular wireless technology, and offers high-speed wireless cellular network connectivity through mobile devices. Wi-Fi is a wireless technology that enables several types of computing devices, including personal computers and mobile phones, to connect to a wireless network through a router. Blending the goodness of both the technologies gave birth to the next generation network technology Unlicensed-LTE. The reason behind adopting Unlicensed LTE is not to overpower the reign of Wi-Fi, but to enhance the spectral efficiency and capacity of 5GHz band by co-existing harmoniously and ensuring fair medium access.

6 ISM bands The unlicensed spectrum bands in the scope of LTE-U technology are the ISM bands in 2.4 GHz and 5 GHz. Of particular interest is the 5GHz band, where large bandwidths are freely available in many regions of the world. In recent times, the fastest growing use of these bands has been for short-range low power communication systems. Cordless Phones, Bluetooth, ZigBee, NFC Devices, and Wi-Fi take advantage of unlicensed spectrum for short-range communication. Audio FM Broadcast AM Broadcast IV 5 GHz IEEE a Extremely Low Very Low Low Medium High Very High Ultra High Super High Infrared Visible UV X-Rays GHz 83.5 MHz IEEE b/g Fig. 2 : Radio Spectrum highlighting ISM bands The rules to access these ISM bands vary from country to country. In the US, FCC defines these rules, whereas, in Europe ETSI is the governing body. In 1985, the US FCC opened the ISM band for radio communication and wireless LANs [1]. What is so special about unlicensed 5GHz band? The 2.4 GHz band all alone has for long time served the wireless world with 100MHz allocated to it. Initially established as an ISM band by ITU in 1947, it has been a powerful enabler to prove the benefits of unlicensed spectrum in terms of high spectral efficiency & wider broadband access (see Table 1). Criterion Range and Performance Number of non-overlapping channels 2.4 GHz Range is higher than that of 5GHz, as waves attenuate much faster at higher frequencies. It has fewer channel options, only 3 non-overlapping. 5GHz Wavelength is half of 2.4GHz, hence has a narrower range. It requires more output power to cover the same distance as 2.4 GHz It has 23 non-overlapping channels. Available spectrum Approximately ~100MHz >300MHz in most of the markets Interference It has higher interference compared to 5GHz It has fewer interference sources. Supported Wi-Fi Version b/g/n ac Table 1 : Differences between two ISM bands - 2.4GHz and 5GHz

7 As the growing use of 2.4GHz has already congested it, the 5GHz band is now seen as a buffer band in the unlicensed spectrum with IEEE latest Wi-Fi version ac working exclusively in this band. Like 2.4GHz, 5GHz is available worldwide with different band boundaries and different regulations. (See Fig. 3) USA Europe & Japan China GHz has one major benefit over 2.4GHz with wider spectrum of > 300MHz in most of the markets. In USA, the 5GHz band has approximately 580MHz In Europe around 455 MHz In China around 325MHz Fig. 3 : Spectrum allocation of 5GHz band across different countries Benefits of using LTE in unlicensed spectrum The main advantages for LTE-U over Wi-Fi as an access technology, stem from better link performance, scheduled medium access control, mobility management, and excellent coverage. These benefits combined with the vast amount of available spectrum (> 300MHz) in the 5GHz band make LTE-U a promising radio access technology in the unlicensed arena. Some of the obvious benefits to the operators are: Increased Bandwidth to serve more number of users, Improved user experience with rich quality of service, Low CAPEX cost for operator as no license fee charged for its use, Unlicensed LTE is fully transparent to the LTE core network, avoiding the need to upgrade any of the Evolved Packet Core (EPC) elements.

8 LTE Unlicensed - Various approaches & related terminology There are different proposals on how to use LTE in unlicensed band and these variants has given rise to lot of confusion in the terminology used around this topic. We use Unlicensed LTE as an umbrella term which covers all approaches of LTE in the 5GHz unlicensed band. Two such approaches are being developed and investigated in parallel LTE-U and LAA. Their acceptance and deployment would depend on how 3GPP specification would mature around them. Characteristics of LTE-U and LAA Both of these versions would rely majorly on Release 10 feature of LTE-Advanced called carrier Aggregation. Both of these versions shall use licensed channel as a primary or Anchor channel which would majorly carry all signalling and control information (See Fig. 8). Whereas, the unlicensed band would be used as a secondary carrier component to augment the data path in only DL (Supplemental DL) or in UL+DL. Table 2 summarizes the differences between two modes of operation. Criterion Integration with Licensed LTE Co-existence with Wi-Fi LTE-U Supplemental Downlink (Carrier Aggregation in Uplink not needed) - Dynamic Channel Selection - CSAT based on LTE duty Cycle - LBT support not needed LAA Carrier Aggregation in UL and DL, using TDD - Dynamic Channel Selection - LBT operation is mandatory 3GPP Release Based on Release 10, 11 & 12 Based on Release 13 Regions supported USA, China, Korea, India Europe, Japan. Being a global approach, this would be compliant with regulatory requirements of most countries. Commercialization Early deployment possible Will be commercialized later, due to ongoing standardization Table 2: Difference between two approaches - LTE-U and LAA The regulatory norms of different countries to access unlicensed spectrum has given rise to two separate markets. They vary in the channel access techniques applied. 1. LBT Market - Europe, Japan: shall follow LAA protocols. The 3GPP is working to standardize LTE-U, under the name LAA (Licensed Assisted Access) in Release 13, which supports LBT in addition to CA. LAA is set to become a global standard, as it targets to meet the regulatory requirements persisting worldwide. 2. Non-LBT Market US, China, South Korea, and India: Here LBT is not mandated, hence operators can roll out LTE-U deployments earlier using 3GPP Release 10/11/12 based specifications. These markets would follow Carrier Aggregation feature of 3GPP Release 10/11/12, which needs changes in LTE Physical layer and does not mandate the support of LBT.

9 LTE-U, The ready to deploy solution for operators In 2013, Qualcomm and Ericsson proposed this version of unlicensed LTE. LTE-U implementation has its basic roots in 3GPP Rel. 10 feature - Carrier Aggregation (CA) with small-cell enhancements in Release 11 and 12. Thus, LTE-U relies on 3GPP Release 10/11/12 functionality with specification designed and defined by LTE-U Forum, an organization established by Verizon in collaboration with ALU, Ericsson, Qualcomm, and Samsung. As it requires fewer modifications from the licensed LTE, LTE-U would be first and the earliest version of unlicensed LTE available to operators. LAA (License Assisted Access), Will it be a fair play? LAA is a global solution adhering to LBT standards of Wi-Fi operation, promising fairness between Wi-Fi and LTE spectrum use. The Release 13 3GPP standardization will integrate LBT with existing licensed implementations. Hence, it would take longer to reach the stage of commercial deployments. Fairness comes at a cost! The integration of LBT will cause degradation in LTE performance similar to the one Wi-Fi suffers from. As the majority of supporters of LAA are telecom vendors and the standardization body - 3GPP too represents them, there have been serious concerns in the industry that LAA would be more favorable to LTE than to Wi-Fi. Beyond all these concerns, there is a serious commitment to find a robust solution for co-existence, where LAA does not levy a detrimental impact over Wi-Fi. The Standalone Version Outlook into the future Currently, the unlicensed access is always anchored in licensed LTE, hence LTE assisted. The standalone version would aim LTE protocol completely utilizing unlicensed band without a licensed anchor. This solution is being promoted as MuLTEfire. The technology now has its own support group in the form of the MulteFire Alliance. However, 3GPP s long-term aim is to standardize a core technology, which must be, as far as possible, frequency agnostic, so that it can be adapted for other frequencies if needed. Unlicensed LTE timelines for standardization and product LTE-U, implemented based on Carrier Aggregation, was introduced in 3GPP Release 10, where ISM carrier can be considered as one Carrier Component. LAA is being studied in 3GPP to standardize a mechanism that guarantees the fair coexistence of LTE with normal users of ISM spectrum. LAA specifications are under development by 3GPP. The estimated timelines as projected by CableLabs' based on recent 3GPP activity with key stakeholders shows that 3GPP LTE Release 13 standardization will go till mid 2016 Chipset standardization expected between Device standardization expected to get complete by 2017 Infrastructure of LTE/Wi-Fi Integrated Small Cells shall start from mid 2017 till end of 2018 LTE vs. Wi-Fi a comparison Throughput and Range LTE provides user data throughput between 100 Mbps and 1 Gbps. The Wi-Fi standards define data rates between 11 Mbps and 600 Mbps. The LTE standards enable connected devices with widespread network coverage, typically nationwide. Wi-Fi computing devices must remain within 300 feet of a wireless router to maintain wireless network functionality. Channel Access In LTE Synchronous Access In terms of channel access, LTE is synchronous and centralized in nature. As it is designed for licensed spectrum, where exclusive use of the spectrum is guaranteed, it is much more efficient than Wi-Fi. Its radio frame duration is 10ms (See Fig. 4). Each radio frame is divided into 10 sub-frames of 1ms duration. Again, each sub-frame is divided into 2 slots of 0.5ms each, which consists of a set of time symbols called OFDM symbols.

10 All LTE transmissions within a cell, both Uplink and Downlink, are assigned to these slots by the LTE base-station scheduler. As scheduling is carried out in a centralized fashion, the UEs belonging to the same cell must be tightly synchronized, both in time and frequency domain. LTE uses the orthogonal frequency division multiple access (OFDMA) the channel access mechanism, which allows simultaneous transmission for multiple users. LTE does not perform carrier sensing like Wi-Fi. 1 Frame (10 msec) 1 Sub-Frame (10 msec) 1 Slot (0.5 msec) Fig. 4: LTE Frame format In Wi-Fi Asynchronous Access (CSMA/CA) Unlike LTE, Wi-Fi takes a decentralized approach to schedule transmissions from different devices. The principle is (1) listen before you talk, (2) if you collide by speaking at the same time with someone else, wait a random time before you try again. Therefore, when a Wi-Fi device wants to make a transmission, it senses the medium and performs a clear channel assessment (CCA) check. If the channel is detected free for, a period (referred to as Distributed Inter-Frame Space DIFS), the transmission proceeds. Otherwise, the Wi-Fi device draws a random number, between 0 and 16 (or between 0 and 32 for b/g), starts a counter and backs-off the transmission during periods when the channel is detected busy. When the counter reaches zero, the device attempting to transmit gets hold of the channel and starts transmission. However, if other devices were also sensing the carrier at the same time and tries to transmit, a collision occurs. When a transmission fails, (which is detected by the absence of an ACK from the receiver), a random back-off number is drawn and the process repeats. With every back off the random counter value is doubled, i.e., increasing as 16, 32, 64 etc. This random access process, referred to as CSMA/CA, is illustrated in Fig. 5. Device A Data Medium Busy Medium Free Data Device B (attempts to send) Carrier Sensing DIFS Random Back off Medium Busy Medium Free Medium Busy Device C (attempts to send) Carrier Sensing DIFS Random Back off Fig. 5: Wi-Fi channel Access, CSMA/CA Collision Device C has longer Back-off than Device B. In addition, when the medium is detected busy, the back-off timer is suspended.

11 Co-Channel Co-existence is it easy to achieve that harmony? The comparison between the two technologies shows that access mechanism in LTE is more aggressive than in Wi-Fi. Wi-Fi being asynchronous tends to be more polite in its spectrum usage whereas LTE allocates the time and frequency resource optimally. Thus, 1. Wi-Fi transmissions are generally not synchronized with LTE transmissions; hence can cause Interference with LTE frames. 2. In addition, if the channel is busy Wi-Fi will defer its transmission leading to starved access. With respect to these two major problems, it becomes necessary to take extra measure to ensure that LTE co-exists reasonably fairly with Wi-Fi while using unlicensed band. Since Wi-Fi devices are already widespread in the 5GHz unlicensed band, there is a need that LTE-U deployments use low power transmission in order to cause low interference to their Wi-Fi neighbors. Hence, early LTE-U deployments shall focus on Small Cell (SC) solutions for harmonious co-existence. To achieve this harmony, two main approaches are under consideration and are discussed in the following chapter. LTE-Unlicensed (Non-LBT markets) Coexistence mechanism for non-lbt markets As the channel is shared by all the devices/technologies, co-existence is the main concern. Without modifying Rel. 10/11/12 LTE PHY/MAC standards, 3 mechanisms can be used to safeguard that LTE is a good neighbor in unlicensed bands (See Fig. 6). Typically, co-channel coexistence techniques in unlicensed bands such as LBT and CSMA (carrier sense multiple access) used by Wi-Fi are based on the concept of contention based access. In these techniques, transmitters are expected to sense the medium and make sure that it is free before starting any transmission. The goal of these algorithms then is to provide coexistence across different technologies in a TDM fashion. 1. Channel selection enables small cells to choose the cleanest channel based on Wi-Fi and LTE measurements. This ensures that interference is avoided between the small cell and its neighboring Wi-Fi devices and other LTE-U Small Cells, provided an unused channel is available. The channel selection algorithm monitors the status of the operating channel on an on-going base, and if needed, will change and select a more suitable one. Channel Selection Secondary Cell DTx Opportunistic SCell Switch-OFF Fig. 6: : Co-existence mechanism for non-lbt markets (Recommended by: LTE-U forum)

12 2. In case when no clean channel is available, secondary Cell (S-Cell) /secondary carrier DTX is applied for adaptive or static TDM for LTE-U Small Cell transmissions based on ms of carrier sensing of co-channel Wi-Fi activities. This ensures that even in dense deployments, the LTE-U nodes can share channel fairly with the Wi-Fi neighbors. 3. In addition, opportunistic S-Cell switch off can reduce interference to Wi-Fi caused due to cell reference signal (CRS) of S-Cells, when their bandwidth is not needed. This decision can be made based on traffic in-activity of users associated with unlicensed band compared to what P-Cell can provide. It is possible since the primary carrier is always operating in the licensed band. CSAT mechanism, an example LTE in unlicensed spectrum uses a mechanism called CSAT (Carrier Sense Adaptive Transmission), which is also in line with the same concept of coexistence based on medium sensing. In CSAT, the small cell senses the medium for longer (than CSMA) duration (around 10msec to 200msec), hence creating longer gaps between transmissions, so that other Wi-Fi devices can detect the medium free and transmit achieving relative fairness amongst the spectrum users. On the other hand, according to the observed medium activities, the algorithm increases or decreases LTE duty cycles proportionally and adapts to the channel conditions.(see Fig. 7) CSAT, in this spirit, is similar to CSMA, except that it has a longer latency. For e.g. in LTE, the base-station may decide to transmit on every other radio frame, which means transmitting in one 10ms frame and then leaving the channel idle for next 10ms with 50% on-off LTE duty cycle. The carrier can be sensed at the granularity of sub-frame level to enhance performance. A modified version of an Almost Blank sub-frame (ABS) feature can be used to implement CSAT when LTE decides no-transmissions. Thus, CSAT is compatible to Release 10/11/12 LTE standards, making early deployment possible in the U.S. markets where LBT is not mandatory. Listen before Talk (LBT) / LAA A global solution To address the concerns from Wi-Fi stakeholders, it is crucial to implement LBT for the success of LTE using unlicensed spectrum. With LBT enabled, each device or access point operating at a given location would scan the channel to detect any activity on this channel and transmit only when it finds the medium unused. This allows different technologies and devices to operate in the same spectrum. There are different ways how LBT can be implemented. For instance, the period between the scans of network activity defined in LAA plays an important role to decide how the traffic will be split between Wi-Fi and LAA. For the same reasons, LAA is supposed to go beyond regulatory norms to achieve the industrial consensus by proving that the impact of a LAA Small Cell is not bigger than that of a Wi-Fi-AP neighbor. LTE in OFF period senses channel utilization by Wi-Fi APs Channel access by Wi-Fi, when LTE off CCA success CCA failed LAA frame LAA - senses Channel Availability LTE ON Duty Cycle LTE OFF LTE ON LTE OFF time Wi-Fi CCA failed Random Backoff CCA Success time Wi-Fi time Fig. 7: CSAT and LBT

13 Co-existence Evaluation (by LTE-U forum) Multiple outdoor and indoor simulations were carried out by LTE-U forum and the results from three companies were evaluated. The exact mechanisms applied for co-existence in different scenarios, conditions for S-Cell turn-off and selection of adaptive or static duty cycle were left to company s discretion. During analysis of these evaluations, it was observed that LTE, when deployed in unlicensed spectrum without any coexistence mechanism, caused significant performance degradation on coexisting Wi-Fi networks. However, when deployed with reasonable coexistence mechanisms, LTE-U behaves as a comparable or better neighbor to Wi-Fi while the total system performance is significantly outperforming a pure Wi-Fi deployment [4.2] One step ahead with LWA (LTE + Wi-Fi link Aggregation Release 13) An alternative to using LTE over unlicensed spectrum that could be much more acceptable to Wi-Fi stakeholders and the broader industry is LWA. This solution targets to enhance LTE performance, thus overcoming the existing disputes between 3GPP and Wi-Fi Alliance over LTE-U/LAA deployments. Qualcomm is strongly promoting this solution. This approach reaches very similar results / goals as set by LTE-U and LAA, by using a different concept. In this, the LTE payload is split and some traffic is tunneled over Wi-Fi and rest is sent over the native LTE connection. LWA uses Wi-Fi APs to augment LTE RAN by tunneling LTE data in MAC frame, so that it looks like Wi-Fi frame to another network, though it is actually carrying LTE data. By this method, both technologies operate in their respective spectrum i.e. Wi-Fi runs on an unlicensed band, LTE continues to run on a licensed band, and they are combined in such a way that there are no changes in their respective access mechanisms. This is the significant difference compared to LTE-unlicensed. Link Aggregation LTE via licensed spectrum LTE via WiFi via ISM spectrum 2.4 GHz & 5 GHz Additional link by tunnelling LTE msg via WiFi ISM 2.4 & 5GHz Spectrum LWA LTE Spectrum 400MHz - 3.8GHz Licensed spectrum as anchor Component Carrier (LTE using ISM spectrum) LTE Spectrum ISM 5GHz Spectrum Carrier Aggregation LTE used in both spectrums LTE-U USA, Korea, India LAA Europe, Japan Fig. 8: LTE-U/LAA & LTE-Wi-Fi link Aggregation

14 Required Changes Unlike LTE-U, that requires new network hardware and new smartphones, LWA would need only software up gradation on user side. User equipment should power up both radios and split the data plane traffic, so that some LTE traffic is tunneled over Wi-Fi and the rest runs natively over LTE. The traffic flowing over Wi-Fi is received at Wi-Fi AP and then tunneled back to LTE Small Cell, which anchors the session. The flows are combined at LTE Small Cell and sent to EPC in UL. Wi-Fi AP also needs to be software upgraded to support LWA, in such a way that it continues to support non-lwa traffic on a separate Service Set Identifier (SSID). LTE-Wi-Fi link aggregation is under study and shall be a part of 3GPP Release 13. Advantages Wi-Fi traffic can benefit from the services provided by carrier operators EPC. Authentication, Billing, Deep packet Inspection(DPI), Lawful interception, Policy and Rule enforcement, etc. LWA, thus, becomes a solution that exploits existing Wi-Fi AP and improves indoor cellular performance. Market Trends, offerings and challenges Service Provider s take towards LTE unlicensed Any kind of addition to the cellular spectrum is always a welcoming step for the revenue generation of cellular service providers. The Federal Communication Commission has already granted Qualcomm, the permission for a small-scale LTE Unlicensed trial at two Verizon Wireless locations in January FCC extended STA (Special Temporary Authority) to Qualcomm in response to its request to test LTE-U equipment at the Verizon trail locations in Oklahoma City and Raleigh, North Carolina [10]. In another initiative, Korean wireless carrier LG Uplus showed its LTE-U trial achieving twice the speed of its commercial LTE-A service, by combining 60 MHz of unlicensed 5.8 GHz spectrum with 20 MHz in the licensed LTE spectrum. Verizon working with Ericsson to add small cells, sees positive results of LTE-U trials With tests conducted by Huawei and NTT DoCoMo, showing LAA delivers better performance in both coverage and capacity, compared with current widely deployed Wi-Fi equipment based on the n standard. A new coalition named EVOLVE was launched in Washington D.C. in September AT&T, Verizon, T-Mobile, Alcatel Lucent, Competitive Carrier Association (CCA), and Qualcomm are the backers of this group. They have formed this coalition to promote the benefits of new technologies like LTE-U and LAA operating on unlicensed spectrum. On the other hand, controversy debates are taking place at regulatory level at FCC over LTE-U Access between Wi-Fi Alliance and LTE-U supporters. Apple, Google, Comcast, and Microsoft who are members of the Wi-Fi Alliance including the cable industry R&D body CableLabs, went to the extent of proposing FCC with certification process for LTE-U operators from Wi-Fi Alliance for deploying LTE-U. Their claims are LTE-U was developed in private, in contrast to LAA and in contrast to standard development methods. Thus, more challenges are lining up for LTE-U than LAA deployments. In spite of all these concerns, market growth is predicted in LTE-U Small Cells deployment. LTE-U Small Cell solution will see early entry in the LTE-U market; a new report indicates that spending on LTE-U Small Cells is expected to reach nearly $2 Billion by the end of 2020 [8] As wireless vendors aggregate more unlicensed spectrum bands, the demand for LTE-U small cells is expected to rise at a compound annual growth rate (CAGR) of 80% between 2016 and 2020, according to the SNS telecom research report. Several large companies operating within the LTE standard, including Verizon Wireless, Alcatel-Lucent, Ericsson, and Qualcomm, will support this growth.

15 OEM s take towards LTE unlicensed Equipment manufacturers take different approaches in their way towards making unlicensed spectrum available to mobile operators to augment their available spectrum. Qualcomm Technologies, Inc. (QTI) The giant chipset manufacturer is promoting and investing into almost all approaches for making unlicensed spectrum available to LTE operators. QTI is moving forward in terms of technology thought leadership. In early 2015, Qualcomm announced support for LTE-U in non-lbt regions for both small-cell and UE products. QTI announced the WTR 3950 RF transceiver, which supports LTE-Advanced carrier aggregation with support for up-to 40MHz channels on handset side. It has announced integration of LTE-U in its FSM99xx SoC, and the availability of the FTR8950 RF transceiver for small cells. For LBT regions, Qualcomm has announced to meet 3GPP standards for LTE-LAA once the specifications are finalized. Qualcomm s new Snapdragon 820 chipset is expected to enable LTE-U in many flagship smartphones in 2016 with upgraded modem (X12 LTE) technology which is designed to choose automatically between LTE and Wi-Fi, depending on signal quality, end-to-end speed, and Internet reachability. It supports LTE Category 12, with theoretical peak downlink speeds of 600 Mbps, and LTE Category 13 theoretical peak uplink speeds of up to 150 Mbps. Overall, Qualcomm is very bullish in its take towards the efficiencies of LTE-U that would improve wholesome user experience and security, while working alongside Wi-Fi as a fair player. At the 2016 Mobile World Congress, Qualcomm showcased LWA, LTE-U, as well as MulteFire. Cisco Systems Inc. Cisco, being a manufacturer of both LTE small cells that utilize licensed carrier bands, as well as unlicensed Wi-Fi technology, follows neutral approach. Targeting to the service provider and enterprise markets Cisco says that its view is that Both Wi-Fi and LTE-U/LAA utilize the band, without significant negative consequences to users of either technology. Cisco views 3GPPs LAA mechanism using LBT with exponential back off as a very positive development and promises to support the work in 3GPP standardization. Broadcom Broadcom has been active in both comments to the FCC and in work in standardization bodies, but is not a part of the LTE-U Forum. Broadcom does not believe that LTE-U as envisioned by the LTE-U Forum meets the normal criteria of a standard [7.3]. Participation in this group is restricted; detailed specifications are not provided, and sharing algorithms are proprietary. Broadcom believes that LAA is likely to be standardized in 2016 and priority focus for 3GPP is supplemental downlink, and that supplemental uplink will be considered in the future.

16 Abbreviations Sl. No Acronyms UNII ISM FCC ETSI LBT CCA LTE-U LAA NFC RFID DIFS VNI ARPU CSAT CSMA/CA S-Cell/P-Cell DTX TDM STA Expansion Unlicensed national information infrastructure Industrial, Scientific and Medical Federal communication commission European Telecommunication Standard Institute Listen before talk Clear Channel Assessment LTE Unlicensed License assisted access Near Field communication Radio Frequency Identification Distributed Inter-frame Space Virtual Networking Index Average Revenue per user Carrier Sense Adaptive transmission Carrier sense multiple access/collision avoidance Secondary Cell / Primary Cell Discontinuous Transmission Time Division Multiplexing Special Temporary Authority

17 References [1] [2] projects/lte-unlicensed/r13-laa-licensed-assisted-access [2.1] Qualcomm (2013): Extending LTE-Advanced to unlicensed spectrum. [2.2] Qualcomm (2013): Introducing LTE in unlicensed spectrum. [2.3] Qualcomm research (2014) LTE in unlicensed spectrum: Harmonious coexistence with Wi-Fi [3] /wi-fi/80211-channels-number-frequencies-bandwidth.php [4] [4.1] LTE-U forum (2015) LTE-U SDL Coexistence Specification [4.2] LTE-U forum (2015) LTE-U Technical Report, Coexistence SDL Coexistence Specification [5] 3GPP TR V13.0.0; Study on Licensed-Assisted Access to Unlicensed Spectrum; (Release 13) [6] [7] & - [7.1] FCC (2015) Office of Engineering, Technology, and Wireless Telecommunications Bureau seek Information on Current Trends in LTE-U and LAA Technology. ET Docket No [7.2] WBA s responses to FCC on seek of information on current trends in LTE-U and LAA. [7.3] Broadcom s responses to FCC on seek of information on current trends in LTE-U and LAA [7.4] Cisco s responses to FCC on seek of information on current trends in LTE-U and LAA [7.5] Google s responses to FCC on seek of information on current trends in LTE-U and LAA [7.6] ALU s responses to FCC on seek of information on current trends in LTE-U and LAA [7.7] Qualcomm s responses to FCC on seek of information on current trends in LTE-U and LAA [8] [8.1] Telecom-v3882/HetNet-Ecosystem-Small-Cells-Carrier / [9] [10]

18 Author Info Sonika Bengani Sonika joined HCL over 4 years ago in the Engineering and R&D (ERS) Telecom and networks division. She has 10+ years of experience in Radio protocol design & development of 3G and 4G technology. Her research areas are focussed on future 5G networks, IoT connectivity infrastructure, and their use-cases. Mirko Naumann Mirko joined HCLs Engineering and R&D (ERS) Telecom and networks division end of Since then, he is heading HCL s LTE Center of Excellence. Mirko has 18+ years experience in telecommunication with a strong focus on wireless. He works in research and development for mobile devices and mobile networks in 3G, 4G, and 5G technology for more than 15 years. Hello, I m from HCL s Engineering and R&D Services. We enable technology led organizations to go to market with innovative products and solutions. We partner with our customers in building world class products and creating associated solution deliver ecosystems to help bring market leadership. We develop engineering products, solutions and platforms across Aerospace and Defense, Automotive, Consumer Electronics, Software, Online, Industrial Manufacturing, Medical Devices, Networking and Telecom, Office Automation, Semiconductors and Servers & Storage for our customers. TM