TDD and FDD Formats

There are two technologies for LTE. For LTE, they have FDD and TDD which both are viable options. Both are viable options. They are both used by carriers in the USA although FDD has been the choice in the past.  

·       What is FDD? FDD – Frequency Division Duplex is something that was used commonly in 3G. It’s paired spectrum with an uplink band and a downlink band in their specific spectrum. For 1G, 2G, and 3G this was common so you could have a talk and receive channel in the system. There is a guard band in between the transmit band and the receive band. FDD was very popular with GSM and CDMA. It is very difficult to take advantage of MIMO antenna technology in FDD compared to TDD.  

·       What is TDD? TDD – Time Division Duplex is where there is one large piece of spectrum used for uplink or downlink. Any part or percentage can be assigned to be the uplink or downlink. If you have 20MHz of bandwidth available, then you’re not locked into 10MHz up and 10MHz down like FDD. Instead, you have full control over how much goes up and comes down. The downside that some carriers had was the timing of the spectrum, and it's higher bands that have this. However, Wi-Fi spectrum is pretty much all TDD, and it works quite well for data. On the other hand, WiMAX used TDD, and it seemed to be taking off but it never fully blossomed and was cast aside for LTE. TDD makes MIMO technology easier to use because it is all in one band. 

So, what can LTE do? It can do both, and it does do both. Just not the same equipment. You could have equipment do either LTE-TDD and LTE-FDD. Both are released commercially as well as part of the 3GPP standard. When you look at the deployments, it helps to know which format will be deployed. You see, FDD may need two antennas or a combiner to work on a tower. While TDD is all in the same spectrum and the same antenna is used for both transmit and receive. The way that today’s radio heads work it isn’t much of an issue anymore because they can handle the formats quite well. In 2016, you still can’t run them together in the same radio head, although the OEMs are working towards that functionality. Antennas are being designed to run both together by adding more ports and more weight to the antennas. 

Note that Wi-Fi is TDD and ZigBee is TDD. Most Bluetooth is TDD. TDD appears to be the choice moving forward. Most 2G and 3G systems were FDD, and they are being phased out. 

Carriers are learning that when everything becomes truly digital in IP format that it will matter less and less for the BTS, but antennas and spectrum efficiency become more important. As of 2016, most of the carriers already have implemented VoLTE into their main networks, all except maybe Sprint who was still relying on CDMA to carry the voice. The carriers know that when they convert VoLTE, it should be the last step to dismantling the 3G networks, saving them money in the long run by retiring 2G and 3G systems. 

4G spectrum, soon to be part of 5G Spectrum

The spectrum is whatever they could get from the FCC in the USA. They get it from the spectrum auctions that the FCC holds. There is always a need for more although some carriers have yet to deploy all of what they have. With 3G they could use smaller swaths of bandwidth. 4G changed that, and 5G will only make them want more. 

Spectrum is tough to show because there is 4G spectrum for auction here in the USA. I realize that spectrum goes to the highest bidder, (in my opinion small businesses suffer). However, the rush to get spectrum has diminished by the carriers learning to make the most of the existing spectrum. While the bands are small, they have been using something called carrier aggregation to combine spectrum bands to look like one big pipe, which is awesome. The OEMs have worked to put together 2 or more bands so that they look like one big band making the end user happy with more throughput.

In the USA, there are many bands. 

•710 to 716MHz paired with 740 to 746MHz used by AT&T 

•746 to 757MHz paired with 776MHz to 787MHz used by Verizon Wireless 

•806 to 866MHz and 869MHz which belongs to Sprint, this is the old Nextel band. 

•1710 to 1785MHz and 1805 to 1880MHz is T-Mobile AWS spectrum. 

•1850 to 1990 MHz is Sprint FDD spectrum. 

•2.5GHz to 2.7GHz is Sprint TDD spectrum. 

•More and more, it would take some time to break them all out. So much spectrum is out there, and the carriers are grabbing what they can. 

5G Network Slicing

Network slicing is 5G’s way to get you everything. You see, one network will not provide all services for everyone, so they have 5G which will encompass many networks, wireless networks, into one big network. You can’t do everything with one wireless network. Like Steven Wright says, “You can’t have everything. Where would you put it?” If you had one network, it would not be efficient enough to serve all the devices on it. You want a network that works. Otherwise, you have a notwork because it does not work! Most IOT devices don’t need broadband. Most smartphones need mobile coverage. Most laptops need broadband. Most gamers need massive broadband to get the VR to work. Each specific group has a different need. Wouldn’t it be nice if you could have several different wireless networks and have them all go into one core and share resources? Well, 5G came up with network slicing so we can do just that!

The research on network slicing showed me one thing that this is a fancy way to say different networks all connected to a common core. I think this term is interesting, but if you are in IT, then you know that you could have multiple networks, virtual or separated, all sharing the same backbone or even the same physical network. The way I see it, it is all about the RAN! Let’s explore why. 

Well, in 5G, it is not much different. The big difference is that you could have a wireless network dedicated to a specific service. What this means is that when planning a network, in this case, a RAN network, make sure you know what the application will be so that you can plan accordingly.

Think about the different markets 5G will be serving. It could be autonomous cars, virtual reality, or tons of simple IOT devices. Each system will have different need and purpose. The goals are not the same for each. Therefore, they should not all share the same network. So, for the 5G network to include them all, they came up with a cool term like network slicing. The reality is that they will all be different networks that could be sharing the same core or even backhaul. We are creating a way to share resources and build in efficiencies.

We’ll get into why in a few minutes, let’s look at how they will work together first. It’s all about sharing of resources. Think of the HetNet, (Heterogeneous Network) and how we had small cells working with Macrocells and Wi-Fi all working together as one network. Now you have multiple networks all working independently, yet, connecting to the common core.

Which resources are shared in network slicing? The backhaul and the core but also routers and servers and possibly even cloud resources. The key to getting latency down is to rely on the cloud. However, the end user will determine which network will be used and how it will be utilized. The way I see it, from a wireless viewpoint is that the device will need to have a wireless network that fits the needs. In other words, virtual reality with need low latency and very high bandwidth to work properly. Autonomous cars will have very low latency but lower bandwidth needs. IOT devices will have medium latency but very low data rates, and they will not be listening to the network all the time like the other 2, they will only listen to the network on a need to know basis. 

The examples above show us that there will be a need for specific wireless networks to serve each purpose. The common denominator will the core. The core will need to know how to process each part of the network. Making the major carriers happy that they have resource sharing capabilities to save costs. They want to reuse as many resources as possible. Device manufacturers will continue to improve devices and battery life. 

Why Narrow Bandwidth systems in 5G?

Narrow band is for IOT devices. You see, with LTE and Wi-Fi, they tend to be on the air all the time which means the device, a smartphone or your laptop, will be listening and processing data all the time. With IOT devices, they don’t need to talk all the time. They could be pinged once a day or even just talk when they have something to say. 

While there are several reasons, the main one is battery life. If it is talking all the time, then the power draw is constant and high. Broadband kills any battery because it is talking all the time. To get a 10-year battery life, you need to plan when or how it will talk and listen. You don’t want it drawing on that battery 24/7 because it’s listening and processing data. Think about your laptop and how the Wi-Fi will drain the battery life, just like the display. These are the main draws of power. Well, with many IOT devices there is no display, so they only massive power draw is the radio. If you can have the radio go to sleep until it is needed or to wake up at a time of day, then the battery will last a very long time. 

For example, if you have a water sensor or a gas meter or a water meter, three devices that could be mounted where there is no available power source, you need to make sure that battery will last a very long time. Each device will have a different function.  

•The water sensor may only wake up to send a beacon to let the system know that it is alive and working unless there is a high-water alarm, then it will send out alerts. This way the battery will only work when it must. 

•For the metering, gas or water, it doesn’t need to send information all the time. Only maybe once a month or when it’s queried. It may send information of the usage is extremely high to let people know that there is a massive draw on the product measured. This way the battery will last a very long time, and the company deploying these devices will not need to run power to everything. 

These are just a few examples of how the narrowband will be a slice of the 5G network.

Why the need for 5G Low Latency?

The key to true 5G high bandwidth needs as well as low bandwidth needs. The quick response for most devices will be needed so that applications can “talk” as close to real time as possible. You may have seen the RTC, Real Time Communication, a term tossed around RTC is where the device needs to react very quickly, and there is little time for delay. For instance, self-driving cars., They must process the data, so when they communicate with the devices around them, they need to have as little delay as possible. I am talking microseconds, not milliseconds. Why? Because they still need time to process the data. 

Self-driving cars won’t just talk to the network, but they will be talking to cars around them, “looking” all around them, driving the car, making thousands of decisions every second, millions every minute. Deciding how to prepare for the road ahead, the environment around them, and what’s the next move. They will always be concerned about what’s next outside the car and inside the car.

Therefore, the communications system must talk quickly, hence, low latency.

What Applications will 5G have?

For one it will have all that you do now on 4G, internet connection, all the apps, all the things you’re doing now that you feel you can’t live without. 

The new applications will push the network beyond the limitations that we know today and into virtual reality and IoT connections and more streaming video that we could not have before. 

One more thing that is driving it? Vehicle to Vehicle communications. It is the thing that we expect to change the way we live. Vehicles that can communicate with each other to make the chances of accidents lower than ever, in theory anyway. It is also pushing the limits of driverless cars. We are hoping that someday in the next five years that driverless cars are commonplace. Can you imagine that? It would reduce the chance of death on the highways and roads in general. The network will be responsible for all of this, albeit more than 5G but the network reliability, latency, and speed. This falls under the Internet of Things, IOT.

In the enterprise, we will have real-time reporting of KPIs, or stock trades, or horse races that we can get real-time results on, even see the action take place in real time.

Sporting events can offer you the best seat in the house at your home, or at a bar or even at any remote location by showing the game in virtual reality. Think about that, watching the game, be it American Football, Soccer or football, baseball, rugby, cricket, or any Olympic event as if you were in the stadium. The only thing you won’t get is the smell of the arena or someone spilling beer on you. Invite me over, and I can take care of the beer spilling part. 

What about smart cities? Suddenly we pushed cities into the idea that they can see all the city at any time. I know you’re thinking that big brother is watching, but what if big brother was looking at traffic patterns, accidents, traffic delays? They may be able to help or at least report it so that you know to go a different way and in real time. They would also see major potholes in the road and warn is that it is ahead. 

The smart home will go to the next level. When the new networks come online, we should have improved battery life with greater efficiency so that we can take the devices out of the home, away from power, and rely on batteries for months instead of days. We could track pets, bikes, anything that we leave outside for a fraction of the cost it would take to do it now. 

Health services for taking medicine and tracking health conditions will improve, we see it now, it will go to the next lever for real-time reporting anywhere and anytime. 

Drones are always brought up, but the network for drones should be large. With drones, they may have a near field 5G connection that would allow them to control and upload and download data. It is the network that will enable these devices to get their information, but they will need to be autonomous at some point. The network can give them the updates and information they need for the flight path but they need to be able to talk to each other in the air, this is where a small 5G mm-wave network can come in handy.