Interview with Liu Ju, Director of Huawei Small Cell Product Line

Huawei is the top supplier of RAN infrastructure worldwide, so it's no surprise they should be in the small cell market. I asked Liu Ju, Director of Huawei Small Cell Product Line, to expand on how he sees the Small Cell marketplace evolving, and what the key technical challenges are. He identifies three critical features for small cells, believes demand will be initially stronger for 3G small cells and explains how WiFi could become integrated into the solution.

Firstly, could you give a short recap of Huawei's view of the small cell market, especially the growing interest in small cells?

For Huawei, small cells are one of the company's top three wireless strategies, the other two being GigaSite and SingleSON. Small cells are so important, as part of the overall mobile network architecture, we have set up a separate organization to focus on them.

When designing any cellular network, we think a deployment strategy should start from a high power macro cell (typically > 10 W), followed by lower power micro (1 to 10 W), pico (< 1 W) and then femto (20 mW) in that order.

In urban areas, public indoor scenarios, urban streets and city squares are the key small cells application scenarios for high-end users in next few years.

What are the critical features of a small cell today?

That's a wide ranging question. Specifically looking at the small cell scenario, we've identified three key aspects:

1) Modular Design

Different application scenarios demand different technology choices, so it's important to be able to choose the backhaul technology and 3G or LTE radio. A modular design allows these components to be designed into the product and manufactured on-demand to meet individual operator needs.

2) Beamforming Radio

Beamforming is a must for network optimization and site flexibility. It helps support RF SON, UL 4 Receiver, high-order MIMO and real-time traffic load-sharing.

3) Wireless Backhaul

We have developed a solution using TDD spectrum, which supports non-line-of-sight (NLOS) and point-to-multipoint (PMP). It's also remotely configurable for low maintenance. Of course, we support all kinds of wired and wireless backhaul solutions with a dock design, which provide Power over Ethernet (PoE) as part of our modular approach.

Which radio technology is in greatest demand? Are you seeing most interest in 3G or LTE small cells today, and how do you expect that to evolve?

During 2013, we expect demand for 3G small cells to become stronger, with LTE demand growth expanding worldwide in 2014.

The market will see cost effective solution for multi-mode 3G/LTE small cells by the end of 2014 or early 2015. Early hardware ready for multi-mode small cells, which only support a single band, cannot avoid duplicating installation and maintenance costs.

What spectrum is most relevant for small cells?

In busy urban areas, it is capacity rather than range that's required. In some countries, we are already seeing macro cells deployed very densely: in London every 400 to 500 meters, in China every 200 meters, and in Japan even closer. In this situation, we don't recommend using lower frequencies (e.g. 700 or 850 MHz) because of the greater interference issues. Instead, we'd expect both 3G and LTE to use higher frequencies, such as 1800 MHz, 2.1 GHz, 2.3 GHz and 2.6 GHz.

Carrier WiFi has been adopted enthusiastically by many network operators, from China Mobile to AT&T and Verizon. How does Huawei see this fit in with cellular service and will future small cells need to incorporate WiFi as standard?

Some operators now want to integrate Carrier WiFi with their small cells, in order to acquire suitable sites, like lamp poles. Huawei already has a dedicated department and product line for Carrier WiFi.

We foresee three steps towards the wider integration of WiFi with small cells:

1) Independent Systems

WiFi networks operate independently from the cellular system.

2) Cellular-Assisted WiFi

Macro cells control smartphones to turn on or off the WiFi receiver automatically.

3) Integrated Cellular and WiFi

The traffic can go in parallel between WiFi and UMTS/LTE while QoS is guaranteed.

What are the key challenges to be addressed before small cells, and especially small cells, become widely adopted? Will small cells be shared between operators?

The key challenges are site acquisition, co-channel HetNet interference control, and backhaul. I discussed earlier the three most critical product features (modular design, beamforming radio, wireless backhaul) that can help solve these challenges.

Competitive pressure will drive widespread deployment during 2013 and from 2014 and the deployment of small cells will blossom. For outdoor scenarios, three to 10 micro cells per macro cell could be deployed.

There has been some debate about whether there will be small cell site-sharing or not. The modular design of our product has the capability to support this, but in the end the market will decide. Different customers have different views on this, with some believing that small cells will be a strong differentiator for them.