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The Rise of the Small Cells & A ‘Brand New Network’?
Uday Mudoi, Vitesse Semiconductor
JUL 01, 2014 01:30 AM
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According to Google Developer Advocate, Don Dodge, the Internet of Things (IoT) requires a ‘brand new network.’ He made some great points at the recent MIT Technology Review Digital Summit, but the linchpin of what he’s really talking about here is small cells. That is, the femto-, pico- and microcells that carriers use to fill in the coverage and capacity gaps in their networks. These are the same small cells that have become so commonplace that AT&T actually has a whole commercial campaign essentially explaining small cells and how they’re using them to improve their network.

Dodge pointed out that IoT connections don’t require much bandwidth, but need to be inexpensive. When it comes to small cells, he’s certainly right that they need to be economical. But, that doesn’t mean that carriers can sacrifice equipment quality. This is a question I’ve heard repeatedly in multiple conference settings – if a service provider is going to use small cells to increase network coverage and capacity, can those cells be of lower quality, essentially cutting equipment costs, than what’s built for macro cells? The short answer is no. Why? It’s all about the consumer. Whether the connection is to a small cell or a macro cell, it really doesn’t matter. Consumers still expect the same deterministic quality of service.

And how do carriers ensure that continuity, so that your cell calls don’t drop or the live streaming of the World Cup on your mobile device isn’t constantly disrupted by buffering? That has everything to do with network timing and synchronization. The reality is that small cells in today’s 4G LTE networks are Ethernet-based. Carriers have two basic choices to provide timing to the small cells: GPS or IEEE 1588 (1588). For macro cells, GPS is viable and currently used. The challenge with small cells, e.g. in an indoor situation, is that there is no GPS coverage. For enterprise-level femtocells, or any indoor small cells in 4G LTE networks, 1588 is the way carriers must deliver timing to the small cell. And because neither equipment vendors will want to build, nor will carriers want to deploy two different types of small cells – e.g. one for indoors and another type for outdoors – essentially ALL small cells have to support 1588 timing.

This leads to yet another obvious and important issue: security. The fact is that as small cells become more widespread, networks are inherently less secure. Located on a lamppost, traffic signal or other ‘urban’ street furniture, small cell equipment is highly accessible and vulnerable. But security is more than just physical location. What about data encryption, protection or even security of the wireless connections themselves? Looking at wireless technologies as a whole, carriers often use IPsec, a Layer 3 Internet Protocol (or IP)-level security. This is common in macro base stations, which are much more physically secured than small cells.

 A major downside of IPsec, however, is that it requires A LOT of processing power, which translates to higher operating costs, power consumption and equipment size. This usually isn’t a problem in a base station, which has far less space constraints than a small cell. The other major constraint is that end-to-end network encryption at Layer 3 is expensive for carriers, in terms of both capex and opex.

As noted above, small cells need to be inexpensive. That makes them extremely sensitive to overall equipment cost, power requirements and size. Especially when the small cell is located on a lamppost or the side of a building, carriers want the smallest unit possible, something that can be powered remotely and that draws as little power as possible. But how can small cells securely encrypt the data without an IPsec processor? The short answer is IEEE 802.1AE security encryption, also known as MACsec, which operates at Layer 2 of the OSI stack. The beauty of MACsec encryption is that it doesn’t need a lot of processing. Traditionally, MACsec has been limited to link-based, box-to-box applications, making it difficult for operators to deploy over networks facing latency issues over multi-hop connections. New technologies, however, implement MACsec in the PHY and allow operators to encrypt network traffic end-to-end at Layer 2. This is especially important as your data travels through third-party networks (i.e. those not owned by your carrier) where the backhaul links are shared by multiple service providers. This flexibility to use MACsec in the small cell networks offers significant capex and opex savings for carriers. And because MACsec is an IEEE standard, the new technologies that allow it to scale effectively for network-wide security are completely interoperable with network equipment from other vendors.

A related challenge for small cells lies in how to secure the data without disrupting the 1588 timing. In my next post, I’ll talk more about that and what carriers and OEMs are doing to solve this issue. 

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