As the demand on wireless networks continues to grow, issues such as spectrum availability and interference can impede a networks ability to support additional coverage and capacity.  This holds true for networks using licensed or unlicensed spectrum.  By considering the use of both unlicensed and licensed spectrum bands, its is possible to support additional growth, while maintaining mission critical access and bandwidth.

Supplementing licensed networks with unlicensed spectrum

Unlicensed frequencies can be unpredictable in coverage, capacity and Quality of Service (QoS) due to the requirement to share the band with other unlicensed users.  However, careful analysis and planning can mitigate the interference issue in most situations.  There are several scenarios to consider when determining whether the use of unlicensed spectrum makes sense.  First, the unlicensed spectrum is used over the same coverage area as the licensed band coverage in order to increase capacity.  A good example is how cellular carriers are now embracing WiFi hot spots and networks to off-load non-critical data traffic from their cellular networks.  This allows smart phones to default to an available WiFi network when sending data, email, and videos, etc.  Cellular carriers are able to offload significant capacity onto relatively inexpensive network infrastructure and essentially free up valuable licensed spectrum for other users. In a similar fashion, many public safety agencies provide their personnel with both a cell phone and a 2-way radio. The 2-way radio is reserved for mission critical communications, often among a group, while the cell phone is used for all other non-critical and backup communications.

Other licensed spectrum users could also consider a similar strategy of leveraging unlicensed spectrum to offload non-critical traffic from their licensed spectrum.  However, for some networks and applications, WiFi may not be appropriate due to its limited range and building penetration.  There are many other unlicensed spectrum band alternatives worth considering, including 900MHz, 3.65GHz and the recently available TV white space spectrum.  In fact, due to its desirable frequency range from 54MHz to 700MHz, wide 6MHz channels,  and good availability in all but the largest cities, TV white space channels may prove to be an excellent unlicensed alternative to WiFi for licensed spectrum users.

Commercial TV white space radio equipment and supporting database systems should begin to appear in mid to late 2010, with trials starting in Q3 2009.  Spectrum Bridge is taking a leading role in the development and deployment of TV White Space solutions. To learn more about TV white space, see ShowMyWhiteSpace.com.

Major Unlicensed Frequency Bands

Moving unlicensed traffic to licensed spectrum

Unlicensed spectrum is widely used for a variety of voice and data applications: including telemetry and site monitoring, family walkie-talkies, CB radios and now ubiquitous WiFi to name just a few.  As shown in the table above there are a number of unlicensed bands to choose from. Range, throughput, equipment availability and cost normally dictate which band is best to use for a particular application.

Traits shared by all of these unlicensed bands:

• The spectrum is free to use by anyone (with an approved FCC radio device)
• The spectrum is shared and you must accept interference from other users
• The maximum allowed transmit power is typically much lower than that allowed for licensed bands

These characteristics of unlicensed spectrum can lead to crowded airwaves, interference, low throughput and unpredictable QoS.  In many instances, unlicensed spectrum users have sought licensed spectrum only to discover it was hard to find, too expensive or unavailable where they needed it.

Spectrum Bridge is addressing these issues by making licensed spectrum easier to find, more affordable and more available.

Our solution is SpecEx, the online marketplace for spectrum™, makes finding available licensed spectrum easy.  SpecEx’s powerful tools let buyers and sellers right-size spectrum offerings to make them more affordable and a better fit for the buyer’s requirements. Repurposing licensed spectrum from its original mission to new applications can also increase the availability and affordability of spectrum and solve scarcity issues being faced in some locations and specific radio service codes. When a repurposed and right sized licensed spectrum solution can be provided, the resultant deployment cost (including the cost of acquiring spectrum) is often less than the total deployment cost of an unlicensed solution. The reason is that the relatively low incremental cost of spectrum can be offset by the need for less radio infrastructure (base stations, access points, etc). Less network infrastructure is required due to the lack of interference and the higher allowed transmit power in licensed bands. This will typically improve the coverage of a single base station or access point compared to those using a unlicensed spectrum.

Combining licensed and unlicensed spectrum to enhance wireless networks

Use of licensed and unlicensed spectrum is usually viewed as an “either or” proposition.  Licensed spectrum holders typically regard unlicensed spectrum has too unreliable from a coverage, capacity and QoS standpoint.  On the other hand, licensed spectrum is sometimes seen as being too expensive or hard to acquire by unlicensed spectrum users.  Spectrum Bridge is addressing these issues with innovative methods to find, manage, acquire and utilize BOTH licensed and unlicensed spectrum.

Optimizing your spectrum strategy

The first step in determining whether to add licensed or unlicensed spectrum to your network is to fully understand how your existing spectrum assets are being utilized.  A few of the questions you need to answer this are:

• Are some channels or areas congested, or underused?
• Do I need additional spectrum to meet the expected growth of my markets?
• Do I have the right spectrum being used for the right applications?
• How do my spectrum assets stack up against my competitors?

These and many other questions must be answered in order to optimize your spectrum strategy and maximize the ROI of spectrum and networking costs. To help with the answers, Spectrum Bridge offers SmartWaves, a comprehensive spectrum asset management suite that provides powerful business analytics and decision making tools to fine tune your spectrum utilization and strategy.