VoLTE

Voice over Internet Protocol (VoIP), when used over LTE, can offer significant benefits to your network— and your business. These benefits include: cost-savings, reduced complexity and hardware, flexibility, and speed-to-deployment. Optimizing VoIP over LTE can also help your employees, customers, and IT teams focus on the work at hand, instead of the mechanics behind it. Furthermore, pairing wired and LTE connectivity moves your mission-critical applications from “three-nines” (99.9%) availability to “fournines” (99.99%) availability—saving you money while increasing customer confidence and brand loyalty.

A common misconception is that VoLTE (Voice over LTE) and VoIP on an LTE network are one and the same. When we talk about Voice over IP in the traditional sense, we’re talking about using either SIP protocol, H.323 protocol, or VoIP to run data across any connection media. The carriers do not see the data traffic as separate VoIP calls. In a traditional VoIP scenario, carriers see voice transmission as data coming from the customer that does not require special treatment. Cradlepoint recommendations will delineate how to surmount these challenges by leveraging the mechanisms on the Cradlepoint router.

VoLTE is a very specific implementation of VoIP on an LTE network, requiring the carrier’s direct participation in the call because the function is using the IMS infrastructure to create the call control and quality. Thus, in a VoLTE scenario carriers are able to distinguish between what is voice and what is data—ensuring maximum call quality. Voice and data are treated differently and have different priorities.

For years, conventional wisdom among IT professionals has held that VoIP promises to enable the next generation of voice communications within the enterprise. However, its adoption has been slower than anticipated. The main culprits have been poor performing IP-PBX systems and the perception that VoIP technology is not ready for prime time. The latest generation of LTE networks means VoIP for the enterprise is now ready for the mainstream.
To successfully employ VoIP over LTE, two prime factors must be evaluated: signal quality and network conditions.

Two metrics are used to evaluate signal quality:

• Signal to Interference plus Noise Ratio (SINR; measured in decibels [dB]; higher result is better)
• Received Signal Strength Indicator (RSSI; measured in decibel-milliwatts [dBm]; closer to 0 is better)

SINR represents how clean the LTE signal is, while RSSI represents how strong the LTE signal is.

The key factors to look for when assessing network quality are latency, jitter, and packet loss.

Latency (measured in milliseconds [ms]; closer to 0 is better) is how long it takes voice packets to go from their original source to their intended destination. For VoIP calls, this round trip process should take fewer than 100 milliseconds. If the delay is too long, the phone call will have pauses while the packets travel over the network and the other person hears the voice; the caller will then have to wait for the response to come back. People often will talk over each other when this occurs, resulting in deterioration of the quality of the phone call and the quality of VoIP services.

Jitter (measured in milliseconds [ms]; closer to 0 is better) refers to the variance in packet delay. If a high volume of voice data packets hit the router at the same time, followed by a pause, and then followed again by more voice packets, it requires the external destination to buffer the data as the packets arrive (instead of absorbing them as a continuous stream). If the network has high jitter, the call quality will be affected in ways that result in issues such as garbling.

Packet loss refers to minimal packets of data being dropped as they travel across the network. Packet loss can occur if the packets are significantly delayed while traversing the network, or if they arrive out of order. Low packet loss helps prevent poor call quality or even dropped calls.

Assuming network conditions are suitable, there are a few simple steps to take to initially optimize VoIP over LTE:

• Verify the network is on LTE and not 3G.
• Ensure a strong, clean signal without interference.
• Know where phones are located on the network and prioritize voice and data traffic.
• Set up Quality of Service (QoS) rules within the router (ensuring voice calls are always given the highest priority when exiting the network)
• Limit the number of simultaneous calls so as to not overwhelm the capacity of the network.

For some organizations, such as a tech support call centers or large outbound-dialing sales departments, VoIP over LTE is not an ideal solution—at least, not with today’s technologies. However, for a small business or small enterprise environment, like a branch or retail store, optimizing VoIP over LTE provides four distinct advantages:

Prioritizes voice data over other data: If an email is delayed by one second, no one really notices.
By contrast, if a VoIP packet is delayed by that long, it can greatly interrupt a phone call. Traffic
identification and prioritization make the distinction between voice data and other data—and how a router should handle each type. By segmenting and prioritizing voice traffic, network administrators can shape the outgoing voice traffic, ensuring VoIP packets have the highest priority and are ushered to the front of the line.

Produces a one-device solution: With LTE, customers can deploy an all-in-one Cradlepoint routing
platform that provides multiple functions: primary connectivity, firewall and security services, and multi-carrier failover. Businesses can save time and money by having a single-box solution.

Establishes carrier independence: Companies are not tied to a single carrier’s network solution.
VoIP on an LTE network allows network administrators to utilize the best carriers in the area or region. Mix and match carriers as needed to provide the best coverage for specific locations.

Enables failover as true redundancy: For many companies that rely on wired connections, such
as a retail location in a mall, it’s likely service will be disrupted in some way or another because of physical damage to wired lines or and ISP outage. When this occurs, LTE automatically provides redundancy as a failover connection. For a small retailer, VoIP over LTE can make a significant difference in ensuring business can proceed as usual. Phone calls and Point-of-Sale (POS) terminals can automatically be prioritized and maintained as mission-critical, whereas other services, such as customer WiFi, can be deactivated until the primary connection has been repaired.

A common question when deploying VoIP on an LTE network is how to take advantage of existing networks to do both VoIP and data. In a traditional setting, a carrier-provided wired broadband connection or other type of dedicated Ethernet connection would be secured, and this primary connection would be used for a mission-critical application. Service disruptions to primary connections expose businesses to lost revenue and productivity while decreasing the quality of the customer experience—and ultimately diminish brand loyalty. Thus, seamless failover is a key factor in the overall connectivity scheme of mission-critical applications.

Many Cradlepoint customers already employ LTE as failover for their data services. A common question is whether they can use—for VoIP (Voice over Internet Protocol)—the same reliable LTE failover that
works for their traditional data applications like POS, email, and web browsing. To answer this question, Cradlepoint performed a variety of real-world application tests. Cradlepoint utilized an Ixia performance test server and client on a PC connected to the Cradlepoint router. This allowed Cradlepoint engineers to control the testing environment and capture the results simultaneously. The G.729 codec was chosen due to its lower data usage and high voice quality.

Each set of tests ran on two different cellular carriers. The tests ran for three days; quality of the connection was decreased each day.

The tests were conducted over a 24-hour period to ensure network load on the carrier networks was taken into account. For each of these tests, engineers ran sets of tests with 1 VoIP call, 5 simultaneous calls, 10 simultaneous calls, and finally with 20 simultaneous calls.

For all tests, engineers ran the tests first as a VoIP-only connection, then added data transfers to the connection to simulate non-voice traffic on an LTE connection.

To express call quality in one broad, overarching measurement, Cradlepoint also calculated Mean Opinion Score (MOS).

As Cradlepoint tests were not intended to determine which carrier(s) may be better than others for VoIP traffic, the carriers will be referred to as Carrier 1 and Carrier 2.

As you can see with Carrier 1 on the MOS graph (Figure 1), MOS remained over 3.6 for the majority of the tests. Only on Day 3, with a higher number of calls and a high amount of data traffic did the quality drop below the minimum MOS threshold.

Call quality was excellent without a network load: MOS was above 3.8. Call quality was impacted by a heavy network load: MOS was good, not excellent. Day 3 (“Poor Reception Day”): Call quality was everely
impacted by heavy network load (cutoff was 10 simultaneous calls).

In Figure 4, the MOS was consistently above the minimum regardless of load until the network
load was exceeded. Figure 5 shows the SINR (how clean the signal is) varied depending on the day. Interestingly, it exceeded the minimum on Day 2 when above twenty calls.

The RSSI (how strong the signal is) dipped below the minimum only on Day 3.

Call quality was excellent without a network load: MOS was above 3.8, except for Day 3. Call quality was impacted by a heavy network load: MOS was good, not excellent; Day 3 was poor, with high calls and network load. Day 3 (“Poor Reception Day”): Call quality was severely impacted by heavy network load (cutoff was 10 simultaneous calls).

As LTE networks become faster, deploying VoIP over LTE is now a viable option for organizations looking to take advantage of existing networks to do both VoIP and data. Given proper network conditions and optimization, Cradlepoint’s testing shows smallfootprint environments can deploy VoIP over LTE as a voice failover solution, just as LTE is deployed for data applications.

Properly configured Cradlepoint solutions offer significant advantages to organizations looking to
streamline voice operations. By setting these parameters, VoLTE becomes a compelling solution: faster call setup times, flexible call location options, and increased call quality.

• No need for network setup: leverage existing LTE cellular connection.
• Better call quality to ensure effective communication.
• Better battery life for mobile devices.
• Cost-savings over traditional solutions.

The Cradlepoint AER family offers distributed enterprises advanced wired and 4G wireless networking performance they need to confidently deliver connected experiences across branch locations.

Rapidly deploy and manage networks at geographically distributed locations with Enterprise Cloud Manager, Cradlepoint’s network management and application solution within the Cradlepoint NetCloud platform.

Necessary Network Conditions

To successfully utilize VoIP over LTE, your overall network conditions must meet several basic quality thresholds. The key factors to look for when assessing your network quality are low latency, low jitter, and low packet loss.

Low Latency: I“Latency” is how long it takes voice data — often referred to as “packets” — to go from their original source to their intended destination. For VoIP calls, this round trip process should take fewer than 100 milliseconds. If the delay is too long, the phone call will have pauses while the packets travel over the network and the other person hears the voice; the employee will then have to wait for the response to come back. People often will talk over each other when this occurs, which disrupts the quality of the phone call, as well as the quality of the services your company is trying to provide.

Low Jitter: “Jitter” refers to the variance in packet delay. If a high volume of voice data packets hit the router at the same time, followed by a pause, and then followed again by more voice packets, it requires the external destination to buffer the data as they arrive (instead of absorbing them as a continuous stream).

If your network has high jitter, the call quality will be affected in ways that result in issues such as garbling.

Low Packet Loss:“Low packet loss” refers to minimal (to no) packets of data being dropped as they travel across the network. Packet loss can occur if the packets are significantly delayed while traversing the network, or if they arrive out of order. Low packet loss helps prevent poor call quality or even dropped calls.

How to Optimize VoIP Over LTE

Assuming your network conditions are suitable, there are a few simple steps you can take to initially optimize VoIP over LTE. If your company is planning on using (or improving on) this system, you’ll need to ensure your business is indeed on LTE and not 3G. You’ll also need to:

• Make sure you have a strong, clean signal without interference.
• Know where your phones are located on your network so you can prioritize your voice and data traffic.
• Set up Quality of Service (QoS) rules within the router (thereby making sure voice calls are always given the highest priority when exiting the network).
• Limit the number of simultaneous calls so as to not overwhelm the capacity of your connection.

For some industries — such as a tech support call center or a large outbound-dialing sales department — VoIP over LTE likely is not an ideal solution (at least, not with today’s technologies). However, for a small-business environment, optimizing VoIP over LTE can provide some distinct advantages.

Advantages of Optimizing VoIP Over LTE

#1: Prioritizing Voice Data Over Other Data. If an email is delayed by one second, no one really notices. But if a VoIP packet is delayed by that long, it can greatly interrupt a phone call. Traffic identification and prioritization make the distinction between voice data and other data — and how your WAN router should handle each type.

This process, also known as traffic shaping, helps ensure that outgoing traffic is segmented appropriately and that VoIP data is always ushered to the front of the line.

#2: A One-Device Solution. With LTE, customers can install and utilize a single Cradlepoint router that provides multiple functions: primary connectivity, firewall and security services along with failover. Your business can save money and time by having a single-box solution, as IT staff can manage one device for all productivity options, and the router can even be installed in a mobile or remote location.

For example, an insurance company that needs to respond to disaster situations can have an entire mobile office on wheels. This mobile office requires both data and VoIP connections to process claims and calls, and it needs to be able to relocate as needed. Wired connectivity may not even be an option, given the extent of the disaster. Additionally, voice and data are both considered critical, as people need to contact the insurance company, provide information, have their claims processed, and begin rebuilding their lives as soon as possible. VoIP over an LTE network helps ensure the insurance company is not hindered by voice and data connectivity issues during the times it matters most.

#3: Carrier Independence.Companies are not tied a single carrier’s network solution. VoIP on an LTE network allows you to utilize the best carrier’s solution in the area or region where you operate. You can mix and match carriers as needed to provide the best coverage.

#4: Failover as True Redundancy. For many companies that rely on wired connections, such as a retail shop in a mall, it’s likely that service will be disrupted in some way or another because of the physical connection being broken (from a nearby construction worker accidentally cutting a cable line, for example). When this occurs, LTE automatically provides redundancy as a failover connection; that’s a general benefit that comes with using LTE as a failover mechanism.

For a small retail shop specifically, however, VoIP over LTE can make a significant difference in ensuring business can proceed as usual. Phone calls and point of sale (POS) terminals can automatically be prioritized and maintained as mission-critical, whereas other services, such as customer WiFi, can be deactivated until the primary connection has been repaired.