In Star Wars terms, the small cells that mobile carriers and vendors will be talking up this week at Mobile World Congress are more like the odd-couple androids R2-D2 and C-3PO than like their foes, the Empire's phalanxes of identical storm troopers.
"Small cells" as a trend is being used to describe both small cellular base stations and carrier Wi-Fi access points (APs), which covers a lot of gear. But those products will be as varied as the different jobs they'll be asked to do. Small cells are carriers' big hope to make subscribers' apps run fast on the busiest streets in town, keep thousands of users online at an arena concert, and give enterprises strong wireless service throughout a corporate campus, among other things.
As a result, small cells can't all look and act the same. They'll be smaller or larger, smarter or dumber, less or more weather-sealed, and based on different technologies, depending on their purposes. Some will even be able to change their stripes in the future.
Big names including Cisco Systems and Nokia Siemens Networks have already talked about the new small-cell products they'll be showing off at MWC, and all are offering an array of different sizes and types of gear. On Monday, Ruckus Wireless will join them, introducing an outdoor Wi-Fi AP and a product that lets carriers bolt together an AP and a cell for mounting on light poles or other outdoor fixtures. Meanwhile, Broadcom will unveil chips designed to power a wide range of small cells expected to ship in volume later this year.
Small cells have to be different so they can work in different settings. In most cases, carrier Wi-Fi will usually stay indoors and small cellular base stations go outdoors, even according to Ruckus, which has built its name on wireless LANs. Complicating that a little, cellular and Wi-Fi may show up in the same place to serve different needs. Ruckus is depending on that with some of its offerings.
Unlike Cisco and some other vendors, Ruckus favors bolting a cellular radio and a Wi-Fi AP together rather than making a special cell to go inside its AP. That's the idea behind the SmartCell 8800 platform it's introducing at MWC. The 8800 puts both components in the same unit for mounting on a site such as a lamppost, with Ethernet connecting the Wi-Fi and cellular halves of the device, said Steve Hratko, Ruckus's director of carrier marketing. The 8800 can use the more spacious 5GHz band on the Wi-Fi radio to backhaul both systems if there are no wires to the site.
This bolt-on approach will make it easier to build "neutral host" setups, where the network owner rolls out all the small cells for a given area, Hratko said. Some governments require this because they don't want lampposts cluttered with multiple carriers' cells. With the 8800, carriers could either share the Wi-Fi radio or each put their own cells in alternating 8800s, taking advantage of the fact that cellular has a longer range than Wi-Fi, Hratko said. The 8800 is due out this quarter.
Ruckus is also introducing the ZoneFlex 7782, its latest outdoor AP, which uses multiple data streams to deliver as much as 900M bps (bits per second) of theoretical shared speed. A version of the 7782 can be set up to serve crowded stadiums by directing coverage beams at individual users when they need them, Hratko said.
Targeting yet another use of Wi-Fi, Ruckus is equipping its smallest APs for backhaul via cellular. Service providers will be able to attach cellular modules to Ruckus ZoneFlex 7321 APs via USB, a configuration aimed at feeding public Wi-Fi services on trains, buses and ferries.
Communications chip maker Broadcom will also have its eye on diversity at MWC as it unveils its latest silicon for small cells. The rollouts include processors for a wide range of small cell types, including ones for homes, small businesses, enterprises and outdoor public access.
For home femtocells, Broadcom has combined RF (radio frequency) and baseband processing in a single chip for reduced size, cost and power consumption. It's designed for 3G WCDMA femtocells that serve eight or fewer users. Another version of the same chip is designed to support 16 users in small enterprises. Those chips are expected to ship in volume in this quarter. For the high end of the residential market, Broadcom is introducing its first chip for LTE femtocells.
Broadcom is also introducing a small-cell chip that can run on 3G WCDMA and be upgraded to 4G LTE, as well as one that can operate on WCDMA and LTE simultaneously. Those chips will support up to 32 users on WCDMA and 128 users on an LTE service where the carrier has 20MHz of spectrum for LTE.
Small cells with both 3G and LTE capability can help carriers deliver better performance for both voice and data, as most LTE operators still carry voice calls over 3G, and improve the experience of all their customers as they upgrade from 3G to 4G phones, Broadcom said.
Taking diversity and flexibility a step further, Broadcom is also introducing a development platform that manufacturers can use to build small cells with simultaneous 3G, 4G and Wi-Fi capability. It's based on the XLP-208 processor that the company got when it acquired NetLogic last year, and it can incorporate other Broadcom chips depending on the manufacturer's needs. The XLP-208 is a multithreaded processor that can carry out extra tasks, such as monitoring for interference, in separate threads. The development platform is due for volume production in the second quarter.