Update to White Spaces.

I spoke with Josh Garza, CEO of GAW High-Speed Internet, this week, and he stated that the Company is currently in the process of deploying a White Spaces network to provide high speed internet to their customers. Good luck to Josh, Great Auk Wireless and their customers, we hope to hear great things about this project.

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Gizmo5, going away. Replacement Service.

UPDATE (4/4): “SIP Registration” Failed Monday. Bye, bye Gizmo5.

UPDATE (3/22): A request to the Support Desk at Gizmo5 has not been answered, but it appears that they may have pulled their STUN Server offline.

UPDATE (3/21): One of our Gizmo5 accounts has failed “SIP Registration” since approximately 2:00 PM today. Maybe they aren’t going to make it until the 3rd!

UPDATE (3/15): We were able to complete the porting of a number from Gizmo5. It required 7 days. This means, don’t wait, if you need this done.

The Gizmo5 VoIP service is closing up shop. We all knew it would happen sooner or later, but it would have been nice to have a little more notice. I got my notice today. I’m talking about the network formerly known as SIPPhone then briefly Gizmo and lastly Gizmo5.

The operation was acquired by Google and was incorporated into the Google Voice product. During their existence, many products and enhancements were offered, some worked well, others not so. Personally, I found some of the products unreliable enough to look for a replacement several years ago.

Having said that, I expect that my two Gizmo5 accounts will be hooked to something until the very end. I use one DID into an VoIP PBX that I built last year and it has worked very well. The other was used as my business line, with an aliased number. If you are one of my customers and I’ve called you sometime in the last three years or so, that was the line that was used. I use another service (see below) for my incoming business lines and my residential service, however.

Back to the replacement issue. I don’t sell anything related to my Microwave consulting practice, I’ve felt that was an appropriate stance, as I want to be “vendor agnostic”. That doesn’t mean I don’t make recommendations or have favorites. It means if a client has something else in mind, I will do my best to get that vendor or equipment to meet his needs.

I have been reselling VoIP services for several years and have many satisfied customers. My web site can be found here: http://www.TollFreeQuick.com  (Not just toll-free numbers) Links from that web page will lead to automated account sign-up, service and number selection. The free internet calling features are available with a simple account. We would be glad to have you use it, please give us a try. If you use a VoIP SIP adapter, phone or PBX with Gizmo5, the transition will be very simple, and the network is very NAT friendly. Again, give this a try with the free account, do some testing and you will be ready when the Gizmo5 service goes down for the last time.

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“White Spaces” – The Database

During the last few days, the FCC released the names of those that will maintain the database for the “White Spaces” equipment. Among them are the major proponents of the new wireless service and each of the databases will be synchronized. The database will be used to determine what channels are available to the equipment.

My opinion is, that there is no such thing as “White Spaces”. Actually, I just don’t like the terminology.

In simple terms the so called White Spaces, are guard bands, placed on alternate TV Channels, on a per market basis, to provide a suitable C/I that will intern, accommodate the integrity of the RF signal. For reference, with analog TV we were looking for numbers in excess of 40 dB, for digital equipment utilizing 8VSB modulation, we now look for C/I’s of better than 28 dB, or so. Many of the proponents had wanted to use the unassigned channels (guard bands) between each channel.

Thankfully the FCC, understood the need to protect the guard bands. As it turns out, in many locations and markets there is spectrum where both channels and their respective guard bands are not used, these will accommodate the new “unlicensed Television Band Devices”. Officially, “TVBDs” and the Rules and Regulations are contained in CFR 47, Parts 15.701-15.717.

I did a quick review of the likelihood of deployments in my own home area, when the Order was first released, and find that it is unlikely that a deployment nearby could take place. Based on both assigned and adjacent channel requirements under the new regulations, I believe that this area is without “White Spaces”. (Channel 48 will be close.) Certainly, this is not the only location that may be problematic. (Southeastern PA.) For you non-TV tech types, a TV channel is six MHz wide.

I’m not sure at this point if the equipment will be sold primarily to Wireless ISP’s or to retail customers. I wonder how this will impact the distribution channels (marketing not frequency) for hardware? How many installers or purchasers of the equipment will find that the wireless devices won’t work simply because the database denies, and rightfully so, the activation of the equipment?

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TDD and FDD

Currently, there are discussions in the Media and most certainly in Boardrooms and Labs about whether forms of FDD should be applied to WiMAX networks and TDD should be applied to LTE networks.

Since it’s once again a hot topic in the industry, I’ve decided to revisit the issue:

An expression used quite frequently in the wireless world over the last few
years is TDD. I would refrain from calling TDD a technical term because it’s more
realistically a marketing expression that’s oxymoronic. TDD stands for “Time
Division Duplexing”. Duplexing in the time domain, isn’t duplexing at all, as those of us
that have been in the radio business for longer than this term has been used, already
know. It is a simplex operation, much like “push-to-talk”, where the channel is shared
by both ends of the communications path. “Push-to-talk” doesn’t sound sexy to most
marketing folks.

Duplex (FDD, Frequency Division Duplexing) systems use different frequencies or
channels for transmission and reception, and the devices used at each end of the
communications path contain duplexers. Duplexed systems require some amount of
frequency separation and the design is based on the amount of circuit “Q” achievable
or economially available, as well as, the amount of available spectrum. They also allow
for simultaneous transmission and reception. Systems that use “Half Duplex” usually
have a duplexer at only one end of the communications path. The 802.11b systems
that we are all familiar with use TDD.

What is most important here is that we understand the significance of the term. Wireless broadband systems that incorporate TDD, have the advantage of operating in
a limited amount of spectrum. A second advantage is that, if we negate the effects of
time, it’s fairly safe to say the propagation path is the same for both ends of the communications link. This second advantage is being capitalized on by some newer systems, which use an adaptive array antenna network to optimize the link from the access point.

TDD is not without it’s disadvantages. Time is TDD’s worst enemy; the system must
switch between transmit and receive, and this takes time. The amount of time depends
on many factors including, but not limited to, the system bandwidth, transmitter power and the ability to predict the exact time to make the transition. Another factor is propagation delay, where the communicating devices must keep the frequency clear for the responding unit while the signal makes “the trip” from one end to the other.

The access point must also have silent periods for service requests from the CPE. The time is dependant on the distance between the access point and the CPE. This system induced latency makes the platform inefficient when compared to FDD systems. If the latency is too great, some TCP/IP clients sense a broken connection. In the case of the old Compuserve, and certainly now VPN’s the browser, email client or a portion of the application must be restarted. VoIP in the form of SIP works quite well when used on many WiFi systems, so the latency is of little concern, there.

A common circuit path can also be problematic, for TDD systems, as it becomes difficult to add amplifiers or frequency converters for the transmitter or receiver individually.

With the aforementioned in mind, can a TDD system be considered “always on”? By
the way, isn’t FDD a redundant expression?

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Site Commissioning

In the Wireless Broadband industry an often overlooked process or issue of diminished
importance is Site Commissioning. In the haste to add customers or prove the
success of an installation, a complete commissioning of the Hub, Access Point or
Base Station is pushed to the “back burner”. Neglecting the Site Commissioning often
negates the rationale behind skipping the step in the first place. Quality assurance
procedures are in place for every successful industry and there is no reason why we
should not plan for success.

The success of the system deployment demands that the design goals be met. The
best method for gauging the success of the installation is to perform a complete Site
Commissioning. The criteria for what constitutes a complete Site Commissioning
depends on the type of platform and complexity of the system. The original design
criteria was based on the coverage, reliability and Quality of Service planned for the
customer. So, these items should drive the list of items to be tested and confirmed
during the commissioning process. The commissioning process rarely adds to the
overall project schedule, and skipping it only lengthens the trouble shooting phase.
During the design process we determine the transmitter power requirements, receiver
sensitivity and dynamic range, the feedline losses and antenna gains. It only makes
sense to confirm that the specifications associated with these devices are met and that
the integration of the devices was successful. Tests at the access point and field
measurements are required to confirm the successful system construction. In addition
to the confirmation process, these tests and measurements provide a perfect
opportunity for the familiarization and training of lesser skilled technical personnel. The coverage testing can provide important marketing inputs.

What kinds of problems are uncovered during the commissioning process? Down
converter gain settings incorrect. Feedlines attached to incorrect antennas or headend
equipment. Antennas installed for the wrong band. Antennas with electrical down tilt
mounted upside down. Antennas pointed at erroneous double digit angles.
Malfunctioning transmitters. Receivers with local oscillators tuned to incorrect frequencies.
Multicouplers with bad splitters. This is by no means a complete list.

Although most of the items I’ve mentioned pertain to the physical layer properties of the system, it’s important to not overlook the customer provisioning aspects. The
commissioning process should include checks to ensure customers are being provisioned in correct cells, sectors and provided with correct QOS levels. Don’t overlook the importance of beta customers with early deployments. They can provide a tremendous asset in determining items to include in a commissioning effort, but make sure they understand their responsibility. I recently heard “I hated to bother anyone since I was receiving the service for free”. As I mentioned earlier about familiarization and training, here is a tremendous opportunity for sales and marketing personnel to become involved.

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Dan Mitten on Wireless Broadband!

Welcome to Wireless Broadband Commentary at DigitalMicrowaveConsulting.com.

As this blog moves forward, I expect to discuss topics for which I have some expertise, namely; Wireless Broadband and VoIP. Oh yes, and from time-to-time express an opinion or two. I’m passionate about my own work and the success of the industry, so join me here, as I progress along this path.

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