Broadband Communities

MAR-APR 2017

BROADBAND COMMUNITIES is the leading source of information on digital and broadband technologies for buildings and communities. Our editorial aims to accelerate the deployment of Fiber-To-The-Home and Fiber-To-The-Premises.

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MARCH/APRIL 2017 | www.broadbandcommunities.com | BROADBAND COMMUNITIES | 25 the cable operator is "moving toward a future where broadband speeds of up to 10 gigabits per second are possible." Verizon now offers a 750 Mbps tier in its Fios markets in New York City, New Jersey, Philadelphia and Boston. AT&T offers gigabit services in many of its markets and plans to add many more, and Comcast is offering a 2 Gbps service in many of its markets. Google Fiber offers 1 Gbps in several cities today. Nielsen's Law, posited by Jakob Nielsen in 1998, states that broadband bandwidth demand grows at a rate of 50 percent a year for high-end users. e broadband connection experience over the years supports his theory. Projecting current trends into the future suggests that 1 Gbps connections will be commonly available before 2020. Median broadband speed, which is less than what is "commonly available," was 41 Mbps in September 2015, an increase of 28 percent over the previous year's median speed of 32 Mbps. If the growth rate continues at 28 percent annually, the median speed will be 100–150 Mbps in 2020, when 5G networks become available, and 1 Gbps at the 5G equipment's end of life eight years later. CAN 5G MEET BANDWIDTH DEMANDS? 5G has been touted to provide speeds 100 times faster than 4G wireless – as high as 10 Gbps – with latency approaching that of fiber. ese speeds indeed sound fantastic! But this projection assumes unrealistic conditions and overlooks the critical fact that the capacity must be shared among multiple users. Wireless vendors often promote their products by listing the fastest data connection rates possible. However, these are theoretical rates possible only in a lab environment and only for a single user located very close to an access point and able to utilize every one of the best-case, unimpaired radio channel resources. is is completely unrealistic for real-world dimensioning for capacity, and it overstates an access point's practical capacity by 500 percent or more. An access point cannot deliver peak speeds across its entire coverage area, or cell. e quality of a radio channel, its spectral efficiency (bits per second per hertz) and its data rate ability deteriorate rapidly with distance, falling to half or less of peak at only 25 percent of the distance to the cell edge. is represents roughly only 6 percent of the cell. To determine a cell's overall practical capacity for broadband, and thus to evaluate the real capability of any proposed network that leverages wireless technology, one must consider the average of the experience among all users near and far. is is often only 15–25 percent of the theoretical peak for a single user. When overheads are considered, the usable capacity will typically be less than 75 percent of this value. It therefore is not unusual for the actual throughput capacity to be only roughly 15 percent of its peak data connection rate – although the latter is the speed that is usually promoted. THREE WAYS TO GET MORE BROADBAND Physics limits the evolution of any wireless technology to three methods: increasing transmit power (or reducing noise), adding spectrum and reducing the number of users per cell. Increasing transmit power or reducing noise. Increasing signal level or reducing noise, including interference, enables better modulation techniques. FCC rules do not permit signal levels (transmitter powers) to increase, and noise will only get worse as more and more transmitters are installed. Without improvement in the ratio of signal to the sum of interference plus noise (SINR), higher efficiency modulation techniques will be usable by only a very few users in each cell, very close to the access point. Providers that use the sub-6 GHz unlicensed bands to offer fixed broadband service today are painfully aware of this. Even with wider channel bandwidths available, they already struggle to support more than just a few subscribers per access point, even at today's fixed broadband users' demand levels, because of the increasing use of video and the uncontrollable and rising noise floor in unlicensed spectra. is will only worsen as the use of Wi-Fi for last-few-feet access by portable devices increases, and as "HetNets," discussed later, emerge. With little or no additional sub-6 GHz unlicensed spectra becoming available, and with SINR only worsening, attempts to increase capacity with higher modulation rates will only shorten cell ranges further, as explained later. For all these reasons, sub-6 GHz unlicensed access points, even if they attempt to use "5G-like" techniques, whether standardized or proprietary, will struggle and likely fall further behind in trying to meet tomorrow's fixed broadband demands in all but the most remote, sparsely used, short-haul applications. In addition, systems that use any unlicensed spectrum are susceptible to being seriously debilitated by competing systems, which can appear close by without warning and without FCC recourse. is renders them risky choices for delivery of any 5G-like fixed broadband, especially if publicly funded. Any significant improvement in wireless broadband performance, then, must be accomplished by adding more spectrum in which interference Actual throughput capacity for wireless users is often only 15 percent of the peak data connection rate – although the peak rate is the speed that providers promote.

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