Metro Wi-Fi

SkyZhone Frequently Asked Questions

What is SkyZhone?

SkyZhone is the industry's first metro Wi-Fi system designed to cost effectively deliver high-capacity, high-reliability, multi-service networks. The system features a number of firsts for a metro Wi-Fi including 802.11n, an all-MIMO antenna architecture, integrated DSL backhaul, and line powering.

Why is Zhone branching out into wireless?

Zhone's customers increasingly want to deliver new and useful service additions to their broadband customers using a variety of access methods. Wi-Fi has become the most ubiquitous wireless interface in countless consumer devices and consequently offers our customers an excellent opportunity to expand their service offerings by supporting devices already present in their service footprints.

I thought "Muni Wi-Fi" has been largely a failure, why a new effort in that?

Careful analysis of the metro Wi-Fi market to-date shows both failures and many successes for a multitude of reasons. Zhone determined that a fundamental improvement in the economic and technical feasibility of metro Wi-Fi could be delivered through many of the features found in SkyZhone, addressing the technical causes of failure in less-successful network designs.

What about WiMAX?

802.16e Mobile WiMAX is a technology which can be both competitive and complementary to metro Wi-Fi. To-date, WiMAX has largely been engineered for licensed frequencies as an alternative to mobile/cellular wireless standards such as Long Term Evolution (LTE).

Who's deployed it? Who's trialing it? How are those going?

SkyZhone has been installed in multiple test installations worldwide serving a broad range of applications including consumer, campus, municipal, and public-safety applications.

For instance, ACD.net, mid-Michigan's largest independent Phone and Internet Provider, selected SkyZhone to deploy networks in the cities of Lansing and Springfield, Michigan. In Lansing, the capital city of Michigan - SkyZhone's all-MIMO design enabled ACD.net to economically deploy a multi-use network serving public safety services using 4.9GHz and high-bandwidth consumer Wi-Fi for video, voice and data in the 2.4GHz band. In neighboring Springfield, ACD.net is utilizing the system to deliver Internet access at subsidized rates for residents in a 6 square mile portion of the city.

When is it available?

SkyZhone is available immediately. What Wi-Fi types does SkyZhone support?

SkyZhone supports IEEE 802.11 b/g/n in the unlicensed 2.4 GHz band, and IEEE 802.11a in the licensed 4.9 GHz band.

What are all the antennas and connectors used for?

The antennas on the top are for the IEEE 802.11b/g/n (2.4 GHz) radio, and the antennas on the bottom are for the IEEE 802.11a (4.9GHz) radio.

One connector is the Ethernet port. This is a 10/100 Bt Ethernet port that can also supply up to 30 Watts of power to a peripheral device. The power capability is described in a later section. Depending on how the unit is configured, this port can be used to manage the Access Point, or it could be used to receive data from an Ethernet device such as a camera.

One connector is for the SHDSL data. These phone lines connect the SkyZhone Access Point to the wired network. The data on these lines can be bonded together to provide over 22 Mb/s service to the Access Point.

One of the connectors is for the serial interface. This interface is used for initial configuration of the unit, and for troubleshooting.

The connectors on the unit are shown in the diagram below.

Why does the SkyZhone have so many antennas?

The SkyZhone uses MIMO (Multiple Input Multiple Output) as defined in IEEE 802.11n. The multiple antennas and the multiple receive paths are key factors in SkyZhone's outstanding performance. SkyZhone uses a technique called Maximal Ratio Combining (MRC). This is a signal processing algorithm that combines the signals from multiple antennas. This allows SkyZhone to see weak signals from laptops and hand held devices.

Why does a MIMO device get better performance?

A radio system that was designed from the beginning with multiple antennas, allows you to take advantage of the Multiple Input Multiple Output (MIMO) technology. MIMO technology increases the bandwidth and range of the wireless signal. It is defined in the IEEE standard 802.11n

As the radio signal travels from the transmitter to the receiver, it reflects off objects, creating multiple paths. In radios without MIMO, signals received on multiple pathways would cause multipath degradation in performance. However, MIMO systems take advantage of digital signal processing techniques to combine the signal from multiple pathways to improve performance.

The SkyZhone system combines the signals received on the antennas to improve the performance. A complex algorithm called Maximal Ratio Combining (MRC) is used to improve performance. A 3 to 6 dB gain can be seen with the MRC algorithm.

Does SkyZhone have an Ethernet port?

Yes. SkyZhone has a 10/100 Ethernet port. This port also supplies power (48VDC) for devices such as cameras.

The slide below shows a camera that is being powered form the Ethernet port on the SkyZhone. The picture on the left is a snapshot from that camera, which is transmitting a continuous stream at 1.5 Mb/s.

How many phone lines are required for each SkyZhone?

Each SkyZhone uses at least 2 phone lines, and could use up to 4 phone lines.

Each of the phone lines is a DSL line. The DSL is SHDSL.bis using IEEE 802.3ah bonding. This type of bonding is called EFM (Ethernet in the First Mile). This type of bonding is based on packets rather than ATM cells.

Each SHDSL link provides up to 5.7 Mb/s of data. With 4 lines bonded together, that provides over 22 Mb/s of data at each Access Point. This is the best backhaul per Access Point in the industry.

What does line powered mean?

You do not have to "plug in" the SkyZhone Access Point. It gets its power from the same copper phone lines that deliver the data.

How is line powering done?

There are 4 phone lines for uplink and line powering. A minimum of 2 phone lines are required for power.

The Line Power shelf sits next to the MALC or other DSLAM and is connected via cable to each 24port SHDSL.bis EFM line card. The line card "injects" the power onto the loops along with the SHDSL.bis signals.

The diagram below shows the installation at the CO.

Does SkyZhone require less access points per square mile than a mesh network?

Typically, Yes. SkyZhone uses the IEEE 802.11n MIMO feature. As a result, the SkyZhone AP has an excellent receiver. It is able to detect the weak signals from the client device, such as a laptop, at a greater distance than access points that do not have the MIMO capability.

Also, the Access Points in a mesh network must be able to communicate with each other in order to form the mesh. Therefore, the units must be close enough to communicate at a reasonable speed.

The SkyZhone solution is principally a star network. Most network nodes have their own backhaul, and therefore has no need to communicate directly with the other Access Points. That means that the Access Points can be put further apart.

Does the SkyZhone use Mesh technology?

SkyZhone networks are primarily based on a star network design, where each Access Point has its own backhaul to the wired network.

However, SkyZhone also supports the Wireless Distribution System (WDS). This feature allows the access points to use the Wi-Fi interface for the backhaul. This allows an access point to be subtended from another access point. This is very similar to a mesh network. A true mesh network would have the routing protocols that allow each access point to discover the other access points in the network.

How does the performance of a SkyZhone system compare to a mesh network?

The SkyZhone system should perform noticeably better than the mesh network. The biggest advantage of the SkyZhone solution is the amount of backhaul. Each SkyZhone node will typically have at least 10 Mbps of backhaul to the wired network. This is considerably more capability than a mesh network would have since the nodes in a mesh network share a common backhaul. This performance difference will be very noticeable in networks that have video cameras or VoIP phones.