Hetnet

Admin | January 24, 2012 | Comments Off

Hetnet

Hetnet

What will come out if you mix femtocell, picocell, metrocell, macrocell, Wi-Fi, cloud RAN and Distributed Antenna Systems (DAS)? Wait, there is more to layer on top of this – 2G, 2.5G, 3G, LTE and LTE Advanced. Well, you guessed right – the Heterogeneous Network (a.k.a. the HetNet) is born. Late last year, I had the pleasure of attending two back-to-back conferences in sunny San Diego, Femtocell Americas and HetNet, both of which featured discussions on this new type of network.

As the names implies, HetNet by definition means disparate networks. If we start to dig deeper, we may find that HetNet is not just the coexistence of different cell sizes or different access technologies or even different network architectures. HetNet is about providing a seamless experience to consumers by the effective usage of technology tools such as Multiple Input Multiple Output (MIMO), Self Organizing Networks (SON), Interference Management, Spectral efficiency, Bandwidth management, Inter RAT mobility, unified security across all accesses, Local IP offload (LIPA) and many more. The HetNet is the vendor community’s response to the “iPhenomenon,” which has fundamentally changed wireless networks forever. Blame it on the simplicity of using today’s smart devices, but it is a realization by operators and wireless infrastructure providers that the onus of counterbalancing the simplicity of devices now lays on their shoulders.

Once a famous scientist named TenTeh (I just made this up, its HetNet backwards) laid out two simple principles–

1) The complexity of wireless network will be inversely proportional to the ease of user experience; and
2) The total sum of complexity in the wireless network will always remain constant.

In last five years or so, handheld devices have evolved to be as simple as possible. Both my three year old kid and my 75 years old grandma can use a smartphone with equal ease and when they are not using it I respond to emails, write and post a blog and can then check how many of my friends like it (too bad there’s no unlike button). This simplicity and multiple usages of smart devices have prompted – A) Increased complexity of wireless networks (TenTeh’s first principle) and B) Rebalancing of the complexity in the wireless networks (TenTeh’s 2nd principle). Who’s getting burdened by all this? It’s the infrastructure network. Guess what, HetNet is just a complexity phenomenon started at the access but slowly it is penetrating into the edge gateways as well. Tomorrow’s gateway will also have to burden their fair share of complexity. Gateways need to be intelligent, adaptive and fast to tackle what HetNets are going to throw at them. More on Gateways in my next blog. At the end of the day, I am relaxed to know that there is a whole community out there, including my own company, Radisys, who is working very hard to solve capacity and coverage issues created by uses like me. You can check out our award-winning Trillium products here to learn more about how we partner with our customers to solve these very issues.

Ericsson, like most of its competitors, has developed a strategy around heterogeneous networks (HetNets). Not surprising, as a leading macrocell vendor, its HetNet strategy is evenly split between the role of the macrocell in the HetNet and the small cell. Ericsson also emphasizes the importance of coordination between the macro and small cell layers. One thing of note with the company is that it defines small cell purely on the base-station footprint. Our attendance at a small cell event just after our Ericsson visit was a reminder that Ericsson’s HetNet vision isn’t shared by all. The small cell show also reminded us that there are vast differences within the small cell community that still need to be resolved. Much remains to be defined, such as the role of the small cell, and the requirements for voice versus data and 3G versus 4G, for example.

Ericsson says size matters when it comes to small cells

HetNet is a wireless industry term generally used to describe a network that combines microcells, picocells, femtocells, and WiFi along with traditional macrocell base stations. In other HetNet visions it can take a more device/end-user centric approach. The combination of multiple network access solutions should help mobile operators deal better with both network capacity and coverage issues. This is especially important as the adoption of mobile communications, and in particular mobile broadband, becomes more common. Most vendors in the wireless infrastructure market have started to formulate their own HetNet strategy, and Ericsson is no exception. We recently had the opportunity to spend a few days with Ericsson, where the vendor took some time to share its HetNet strategy with us. Like any strategy, much of what it contained was forward looking and provided guidance on where the vendor was going and touched on things currently not available. Ericsson remains firm that it does not see a substantial market for residential femtocells, but does see opportunities for the larger enterprise-grade femtocell. The company also sees a role for WiFi offload as part of the HetNet.

The key for a successful HetNet deployment, in Ericsson’s opinion, is coordination between the macro and small cell layers. This coordination can be either tight or loose. Coordination between the layers is needed to ensure maximum capacity at the network edge. While much of this fits in with other vendors’ views of the HetNet, one area where Ericsson differs is its vision of the small cell. For Ericsson a small cell is based purely on the base station’s footprint, whereas other vendors and operators also add in base-station power output and backhaul requirements as part of their small cell definition. Thanks to this distinction, Ericsson can point to commercially available solutions such as its AIR (antenna integrated radio) and main remote base stations, allowing the company to start implementing its HetNet vision with operators.

Small cells deployed already but not yet as HetNet

We also recently attended the Small Cells World Congress in Berlin where carrier and vendor attendees expressed interest but also shared many questions about small cells. There was agreement that small cells are the best hope to support rapidly growing but unevenly distributed mobile broadband data. But the discussion was complicated by the scope. Not only do product categories range from micro to pico to femto, but there is no common agreement on definitions of these categories. The requirements varied for indoor versus outdoor scenarios, enterprise versus consumer needs, voice versus data, and 3G versus 4G.

The meeting also highlighted that experience to date is limited: while there have been some small cell deployments already, these have largely been for indoor coverage. Some speakers stated that their SONs (self-organizing networks) were operational, but we believe the plug-and-play functionality they referred to is just the beginning of where HetNet is going. Deutsche Telekom’s was the clearest voice, articulating that it sees a gap in the industry’s definition of solutions needed beyond the next two or three years.

There is lots of work left to be done in the small cell market

Messaging coming from Ericsson regarding small cells and HetNets along with its competitors’ messaging on those topics show that while there is growing agreement on the importance of small cells, there still remains much that needs to be done when it comes to defining the overall small cell market. But Ericsson’s focus on coordination between the different layers of the HetNet appears to be something the market needs to address. The macrocell in no way is going away. Multi-vendor HetNet solutions can be difficult to coordinate.

So far, most vendors coming to the HetNet from a small legacy base have downplayed the importance of the macrocell. BelAir’s 2100 Metrocell is an interesting exception. The 2100 allows the macrocell vendor to insert its own radio into the BelAir’s small cell solution, thus allowing tighter coordination between the two network layers in the HetNet. This ability to coordinate will be important no matter what shape the small cell/HetNet market takes.