Over the past year, LAA development has quietly matured with several commercial network launches around the world. Offering superfast Gigabit data rates, the technology is ready to be rolled out in-building. We review the current state of the ecosystem and share some insights from SpiderCloud who have been an early pioneer of the technology.
LAA State of the Nation
LAA makes use of unlicensed 5GHz spectrum (typically used by Wi-Fi) to boost speeds and add capacity to existing LTE data sessions. Your phone still has to be connected through licenced LTE spectrum and LAA enhances the downlink data rates. Blazingly fast speeds are possible, aggregating several 20MHz channels to achieve more than 1Gbps data rates.
Unlike LTE-U, which used predetermined on-off periods to transmit data in the 5GHz band, LAA “plays nicely” with Wi-Fi by listening out for Wi-Fi devices before transmitting. This has become a 3GPP standard and can be used worldwide.
In the US, earlier last year the FCC authorised the launch of LTE-U with both Verizon and T-Mobile launching service in Q2 2017. In November 2017, both Verizon and T-Mobile confirmed they were switching to LAA. AT&T have always pursued only LAA, delivering 750Mbps speeds in San Francisco. Sprint have been very quiet but in December announced success with SpiderCloud using only 5MHz of their licenced LTE spectrum. Their CTO confirmed LAA was part of their long term roadmap.
I suspect that most if not all LAA deployments to date have been outdoor using standard Nokia, Ericsson and Huawei base station equipment. Several antenna vendors have launched products that support both 3.5 and 5GHz bands in addition to the regular sub-3GHz cellular frequencies.
The most common configuration is one LTE 20MHz channel with up to 2 unlicensed 20MHz channels (called 3CCA) but Verizon and Ericsson have been looking ahead at up to 5 LAA channels (called 5CCA). A combination of 3CCA, 4x4MIMO and 256QAM can achieve 1.175Gbps in ideal conditions.
The internal chipset to look out for is Qualcomm’s Snapdragon 835 processor and X16 modem which combines 256QAM, 4x4 MIMO and 3CA LAA capability to achieve 1Gbps. This is found in the Samsung Galaxy S8, HTC U11 and Moto Z2 Force.
Qualcomm are naturally keen to promote the technology and contrast the performance of a Category 16 smartphone (such as Samsung/HTC/Moto) with a Category 12 device (such as an iPhone).
The iPhone 7 shipped with either an Intel or Qualcomm chipset for various reasons. The latest iPhone 8 and iPhone X do have a Qualcomm X16 but don’t yet support 4x4 MIMO or 5GHz LAA. Perhaps that will come in the next iteration later in 2018, otherwise peak cellular performance may be perceived to lag behind that of the Samsung and other Android products.
Indoor/Enterprise LAA ready for service
I’ve seen several enterprise small cell vendors announce or launch LAA capable products. The technical engineering involved is somewhat more advanced than just introducing a new frequency band such as 3.5GHz CBRS. LAA builds on Carrier Aggregation, adding multiple supplementary downlink channels on demand to boost speed and introduces Listen Before Talk(LBT) technology used by traditional Wi-Fi devices.
Traffic can’t be entirely offloaded from licenced spectrum, so in many cases mobile devices with limited traffic demands may rarely use it. Voice calls would almost certainly be retained on the licenced spectrum to ensure quality of service. LAA will be ideal for continuous video streaming and large data downloads including App updates.
Contrast the two charts below. The top one indicates traffic demand, with burst demand at times. The bottom one shows how that might be handled by an LTE-LAA solution, where normal traffic is retained on the licenced LTE bands with peak traffic demand activating the LAA supplementary channels as and when required.
Co-ordinating with the natural chaos of Wi-Fi
Cellular systems benefit from dedicated and exclusive spectrum that shouldn’t be used by anyone else. This allows planners and system designers to pre-assign frequencies and RF power settings to optimise performance. While the presence and demand of individual cell phone users at any specific time can’t be predicted, the available capacity and system performance is well known.
Wi-Fi systems are intended to be more ad-hoc and quickly adapt to changes. While professional engineered and designed systems in offices and public venues can achieve high performance, they are still at the mercy of any Wi-Fi smartphone hotspot that may pop-up and any other nearby uncoordinated Wi-Fi equipment. This makes it considerably more difficult to accommodate and plan for sustained reliable performance in busier environments.
Larger enterprise Wi-Fi deployments have their own SON (Self Organising Network) functions that centrally orchestrate the band plan/channel allocations used by each Wi-Fi access point. Nonetheless, each access point must actively “listen-before-talk”, sensing any other transmission in a channel before starting to use it. This requires some local intelligence, typically built into the hardware itself.
As one of the early pioneers of LAA, SpiderCloud have incorporated similar techniques into their LAA radio nodes. A dedicated Wi-Fi chip doesn’t just listen to other transmissions but actively decodes Wi-Fi beacons, identifying when and which other devices are about to transmit. It also uses listen-before-talk(LBT) protocol that resembles Wi-Fi’s carrier sense multiple access with channel avoidance to better co-exist with existing Wi-Fi deployments. This works well at the physical layer, interworking with other Wi-Fi and LAA equipment using the same well known protocols and methods in use today.
Additionally a centralised SON software component aggregates known use of each 5GHz channel and calculates an optimal band plan for LAA use. Each Radio Node has a different unlicensed channel ensuring optimum performance for LAA network. Centralized SON algorithm also eliminates the need for any careful planning with existing Wi-Fi networks. The channel assignment per Radio Node is periodically refreshed to accommodate changes in traffic loading and usage within the E-RAN system as well on the Wi-Fi networks
Simulations indicate that an extra 20 to 30% system wide performance improvement is achieved by use of centralised SON compared with independent standalone ad-hoc operation.
SpiderCloud’s straightforward deployment model, using standard Cat5 structured cabling with Power over Ethernet, typically places combined LTE-LAA radio nodes throughout the building connected to a single controller. Where more than one network operator is to be supported, a separate set of radio nodes with full LTE-LAA capability would be deployed. For those enterprises with existing Cisco Wi-Fi access points, clip-on modules can be used to expedite installation. A “hopscotch” approach with every other Access Point connected to alternative network operators provides adequate coverage and performance for two or more operators.
The timescale for wider LAA deployment now depends on how quickly network operators approve and deploy this technology, as well as expanded support across the more popular high-end smartphones.
SpiderCloud’s SCRN-320 LTE-LAA radio node is already approved by Verizon and can be purchased directly by an enterprise.
The US does seem to be the leading market for LAA to date, with strong marketing highlighting the peak data rate through the moniker of Gigabit LTE. Other regions are waking up to this opportunity.
Operators will need to formally certify and approve small cell equipment, such as SpiderCloud’s, to encourage wider take-up indoors. This should be easier for those who already support the vendor and will radically increase the maximum capacity of in-building cellular systems.
SpiderCloud was acquired by Corning in July 2017.
Find out more about SpiderCloud’s LAA solution from their website
For those with strong technical interest in LAA Wi-Fi co-existence, this independent research paper may be useful.