Darren, You provided a useful update on the interest in and some parameters of wireless cable. Just a couple of comments:
<Just like wired cable, a 6 MHz wireless television channel can support 27 Mbps of downstream data throughput using cable modems with 64 QAM (quadrature amplitude modulation) technology. Historically, a telephone-return path has been used for upstream communication, but operators are now transitioning to full two-way wireless delivery.>
Historically true. QAM64 with its line of sight requirements (~26dB C/I requirement in the totality of the point-multipoint 2.5GHz system link budget actually is what produces the LOS requirement) is problematic into foliated residential areas. That has spawned some interesting CDMA cellularized approaches that require a substantially lower C/I. It remains to be seen if this approach overcomes the LOS requirement with a useful level of success. The 2.5GHz signals don't burn through trees any better when you change the modulation, but the demands for recovering the signal are much reduced. BTW, note that cellularization, by itself, is no solution to the LOS problem. Just think about it -- if you need LOS in one specific direction from the customer location, and it is obstructed, it does not matter that the downstream signal is from a low power cellularized transmitter rather than a single metropolitan transmitter. In fact, the cellularized transmitters are probably at a lower elevation than the single metro transmitters, which could exacerbate the LOS problems (but not much in reality -- the height of a metro MMDS transmitter still gives elevations at subscribers that are too low to clear most trees.)
The words about WCS are correct, but the industry has not and probably will not ever consider WCS spectrum blocks to be a part of wireless cable spectrum, as in the table below. It simply will rarely be used in this way, the Bell South WCS spectrum swap notwithstanding.
>2.150 - 2.162 GHz MDS 2 6 MHz
>2.305 - 2.320 GHz WCS 2 5 & 10 MHz
>2.345 - 2.360 GHz WCS 2 5 & 10 MHz
>2.500 - 2.596 GHz ITFS 16 6 MHz
>2.596 - 2.644 GHz MMDS 8 6 MHz
>2.644 - 2.686 GHz ITFS 4 6 MHz
2.686 - 2.689 GHz MMDS 31 125 KHz
>In the U.S., traditional wireless cable system operators have >aggregated available MDS, MMDS and ITFS spectrum in a given market, >providing up to 200 MHz of bandwidth, the equivalent of 33 analog 6 >MHz television channels.
This is nearly true, but it implies a situation that is far from true. In the top 50 markets, there are indeed 33 channels between the MDS, MMDS, and ITFS allocations. It is relatively rare for a system operator to have aggregated all of these "available" channels. Some are not really available, e.g., ITFS channels in use by an educational institution, but some are, the operator just could not get to lease terms with spectrum owner, perhaps the proverbial "doctor and dentist" who got his name into the lottery back in 1983-84. Many rural systems operate with 12-16 channels; big city systems generally operate with 25 channels or more, but rarely more than 30 - 31.
The IXCs that just "discovered" MDS spectrum presumably have done their homework and already understand the challenges they will face in deploying a widely available high speed data service in residential communities. Personally, based on recent associations with some of their business development and engineering staff, I don't presume anything anymore. Maybe this is not a residential play at all, apart from serving urban MDUs. Time and technology developments will tell. |
