Over the past year or so, 5G has become a hot topic of discussion in telecom industry, with several operators rushing to make premature announcements. But in reality 5G hasn’t been defined, and commercial user equipment is not expected to hit the market until at least 2020.
Initially, Verizon had a rather optimistic 2016-2017 timeline for their 5G commercial product, but quickly reverted to a more relaxed projection involving a fixed broadband solution targeted for 2018. Why all the hype then? Well for one, competition in the wireless industry has never been more fierce, and any perception of technological competitive advantage could be used for marketing purposes. Furthermore, 5G mmWave rollout will not resolve short term capacity issues US operators are likely to face in ’17 and ’18. Once standardized and commercialized, 5G looks to be a hotspot-like application at best, deployed mainly in areas of high capacity demand in dense urban environments, and it certainly won’t solve pre-existing coverage issues. This is why the existing macro cell grid and a good ole’ LTE technology will continue to be the main workhorse for some time to come. This is also why it’s crucial for operators to rapidly refarm their legacy spectrum assets, and densify the macro layer as soon as it’s possible.
At the time we are writing this article, in New York City market, Verizon has a whopping 90MHz of LTE spectrum commercially deployed, AT&T 40MHz, (70MHz in limited hotspot locations with Band 30 and Band 29), T-Mobile 50MHz soon to be 60MHz with Band 2 refarm, and Sprint 60MHz, but 80MHz projected for 1Q17. A simple glance over these numbers would lead us to believe that their performance should be comparable, but that’s actually far from the truth.
Enter the macro site density. For decades, the original low band cellular licensees Verizon and AT&T have been serving their voice subscribers with the least acceptable amount of cell sites in order to maximize the profit. With their initial 700MHz LTE overlay and low amount of LTE users, they didn’t have to spend too much time and resources on network dimensioning, as it perfectly matched their existing low band site spacing. Fast forward five years, and they’re scrambling to densify in order to address the exponential growth in mobile data consumption. Sprint also has a lot of catching up to do as they’ve been relying on in-market CDMA roaming agreement with Verizon for way too long. My hope is that they can figure out how to integrate legacy Clearwire sites, massive swaths of 2.5GHz spectrum, and finally execute on the deployment. In order to provide ubiquitous coverage and capacity on all LTE layers and a compelling end user experience, operators will have to prioritize their densification efforts. Small Cells are soon to play a very important role in providing incremental capacity, and will surely be the driving force behind 5G, but without a dense macro foundation fully in place today, it will only get harder to match the coverage width and depth, and meet customer’s high expectations.
T-Mobile is an interesting case study. After transferring 10MHz of PCS spectrum to Cingular back in 2005, T-Mobile ended up with only 20MHz of spectrum in New York City and millions of domestic and international customers to serve. At that time, in order to survive and stay competitive and without low band assets in their spectrum portfolio, their only option was to build a cell grid denser than anything ever built in this country. At the time most industry analysts and vendors advised against the move, predicting that it would do more harm than good, but managing a tightly spaced GSM network early on turned out to be invaluable for T-Mobile.
Fast forward to a decade later, and this strategy is paying off with massive interest. In this day and age, closely spaced macro site grid with smaller cells is their key enabler in delivering the fastest LTE data rates for well over two years. Over the years they’ve added 50MHz of AWS spectrum to their portfolio, and with more cell sites covering the geographical area and less users pulled in by an individual cell, T-Mobile is able to provide more capacity per subscriber and higher data rates. Also, 700MHz overlay on an existing dense midband grid seems to be adding additional value to what’s already a compelling user experience.
So in the short term, what could operators do to address the exponential growth in mobile data consumption? Well, they could start by activating Higher Order Modulation both on the Downlink and Uplink, since it typically only involves a simple software upgrade and it’s capex conscious. Going from 6 bits per symbol to 8 (64QAM to 256QAM) on the Downlink yields a 33% incremental capacity gain, while the increase from 16QAM to 64QAM on the Uplink corresponds to a potential 50% gain in throughput. It’s important to note that in order for users to get 256QAM frames scheduled, Signal to Interference + Noise Ratio needs to be high. This means that only devices close to the center of the cell will be able to see increased peak data rates, which is a relatively small number. But because those users will be able to complete their data tasks faster, network will be able to free up those resources and redistribute them back to all users (including the ones without 256QAM capable devices) more efficiently. Also worth noting that vendor specific, advanced interference mitigation solutions like Ericsson Lean Carrier have already been commercially deployed.
Another option is enabling Higher Order MIMO, 4×4 MIMO in particular, which could double the peak data rates by doubling the amount of independent spatial streams (from 2 to 4) sent from the cell site to the user. Depending on the infrastructure vendor, this will likely involve upgrading the equipment at the cell site. By virtue of having four transmit antennas at the site and four receive antennas at the user device and vice versa, signal resiliency is highly improved specifically in cell edge situations.
On the user side, capable devices will have to be seeded to market, but luckily Qualcomm’s Snapdragon X12 modem has been readily available and shipping in volume as a part of Snapdragon 820. Among the plethora of impressive cutting edge capabilities, X12 supports 3CC Carrier Aggregation, 4×4 MIMO, 256QAM on the Downlink, 64QAM on the Uplink, Uplink Carrier Aggregation, just to name a few. It’s now up to operators to request at least 4×4 MIMO and 256QAM capabilities when ordering their upcoming flagship devices from the leading OEMs.
In one of our future articles we intend to quantify the benefits of these important LTE capacity enablers. Stay tuned…