In a recent Rohde & Schwarz webinar, Wade Sarver, Nokia Services Solution Manager, presented on C-Band Deployments, Architectures, Practical Considerations and Testing.
C-band has a long history of being used by satellites, AT&T Long Lines Transport, and Microwave downlink for TV, Sarver said, but it hasn’t been used efficiently recently, which opened the door for the FCC to auction spectrum from 3700 MHz to 3980 MHz for 5G. In Auction 107, Verizon won the most spectrum and pops, 161 MHz and spent over $45 billion.
AT&T already has about 17 C-band-capable devices available today using about 80 MHz of spectrum that it spent over $23 billion at auction. UScellular, a regional carrier, spent $1 billion on 252 C-band licenses, or 10 MHz of spectrum, in 99 geographical areas covering 94 percent of its subscribers in the 21 states.
Other C-band spectrum that has been auctioned by the FCC includes 3,550 MHz to 3,650 MHz, known as the Citizens Broadband Radio Service Priority Access Licenses in Auction 105, and 3,450 MHz to 3,550 MHz in Auction 110.
More recently, C-band has been in the headlines because of fears that it would interfere with the radar altimeters on landing aircraft, which delayed the transmitters from being turned on. Although carriers are still lowering the power of transmitters near airports, currently 90 percent of all of the radio altimeters have been tested and received no interference. Nevertheless, the wireless industry has rapidly moved forward with its C-band deployments
Sarver updated the audience on the timeline of the C-band deployment. In the fourth quarter 2021, the industry completed planning and prep, including core and site planning, and began site acquisition. In the first and second quarters of this year, deployments have ramped up for both macro tower sites and urban small cells. The second half of the year will see full deployment activities. Next year and beyond, testing will begin, deployments will continue, suburban markets will be turned on, and sites will appear in rural areas where it makes sense.
C Band Will be a 5G System
Although, in other bands the carriers are migrating from 4G to 5G, Sarver noted that C-band is unique because all deployments will begin as 5G networks from day one on that spectrum.
“Deploying it as 5G standalone provides all the benefits of 5G, as opposed to 5G non standalone where 4G and 5G have to share the core,” Sarver said. “So as new 5G services come out, as new 5G functionality comes out, as new 5G apps come out, they can just deploy them. There’s nothing to hold back, which is really cool.”
CBRS spectrum can be used to aggregate C-band spectrum, so the two bands may be co-located or CBRS could be deployed nearby in small cells to extend coverage and increase throughput, according to Sarver.
“Distributed RAN (DRAN) and Concentrated RAN (CRAN) will continue to exist because the OEMs have not moved away from making baseband units, but expect more migration to CloudRAN in the future,” Sarver said. “Standalone 5G networks will allow carriers to migrate from DRAN and CRAN to OpenRAN.” Adding vRAN functionality allows AI, which can improve latency, reduce routing issues, and improve end user experience, he added.
This is the start of carriers adding OpenRAN to break apart the backhaul, then adding longer fronthaul and mid-haul, Sarver said. 5G SA cores will enhance the 5G capabilities, which means it will most likely be a Cloud core and make use of Edge servers.
C Band at the Cell Site
C-Band will bring many changes to the cell site. First, almost all the antennas will be integrated mMIMO. “You may see CBRS and C-band remote radios connected together into the same radio/integrated antenna,” Sarver said. “You will see 3.45 GHz, CBRS and C-band systems collocated in most new sites, and you may see the sector counts jump from three to four, five, or six to accommodate for better coverage.”
Mini-macro and small cell fill sites may use C-band along with CBRS as the network grows, and as C-band matures, the BBU may not be a traditional BBU, but a smaller rack mounted unit. Edge servers will eventually be located at most sites and poles along with stand-alone edge server boxes.
“Edge micro data centers will grow and become commonplace to support 5G deployments,” Sarver said. “Carriers are going to use edge servers more than ever to offload that local traffic in the C-band.” Eventually, edge servers will be deployed at every cell site, and “quite a few” are already deployed, he noted.
Testing Requirements for 5G C Band
Sarver said it is important to know C-band testing goes beyond coverage to include data testing, uplink and downlink speeds, latency, throughput, among other things.
Tests must be completed between C-Band and the other 5G spectrum, whether it’s millimeter wave or CBRS. “Once up and talking, the gNodeB needs to be tested for carrier aggregation for New Radio, 5G only, but between TDD and FDD as required. Testing may be required between technologies and bands with dynamic spectrum sharing.
If there is voice, VoNR (Voice over New Radio) test calls will need to be tested. E911, 911 calls have to be tested and proven, either simulated or real. Drive testing will be required in the beginning, but not on an ongoing basis.
“As you’re doing the site acceptance at any C-band site or any 5G site really, you have to make sure you’re doing the proper test and you log everything,” Sarver said. “You have a lot of spectrum and it is TDD spectrum. You have to make sure the uplink and the downlink are what the carriers want. It’s very important that you understand what carrier specifications are for the testing.”
This webinar is available On Demand.
By J. Sharpe Smith, Inside Towers Technology Editor
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