We will now look into mobile communications and focusing first on the evolution trend. We start off with AMPS, Advanced Mobile Phone System. It is a first generation mobile cellular phone. This is where the cellular phone, the mobile phone all began. These technologies are based on FDMA, Frequency Division Multiple Access and analog which means that the overall channels were divided into sub channels of frequency based on Frequency Division Multiple Access and within a channel, the signal was sent in an analog way. What do we mean by analog? Typically the options that we have are frequency modulation, phase modulation and of course combining in some cases, amplitude modulation. These were developed by Bell Labs and introduced in North America in 1983. Then we go into GSM, Global System for Mobile Communications. This is the second generation of mobile cellular phones and this is based on digital technology. It was introduced in Finland in 1991 and it became a dominant global standard because once you go into digital, then you have a couple of additional features that you can do. First, a digital system in wireless communication can provide error detection. If there are errors in the communication, you can find where they are and using that, the reliability of the exchanged information goes up. Number two. You can do compression. Number three. You can do Time Division Multiple Access which gives us a great advantage and we will soon see that. This is because once you do TDMA, Time Division Multiple Access from the overall channels divided into sub frequency channels. Within one channel, now you can have multiple users sharing that one sub channel based on time. It dominated the market, over 90 percent, and operated in over 219 countries and territories throughout the world. GSM uses FDMA and TDMA combined. FDMA is Frequency Division Multiple Access so therefore the overall frequency channel that is assigned is divided into blocks and these are sub channels. Now before in first generation mobile cellular communication AMPS, one of the sub channels had to be assigned to one user. So therefore it was very inefficient but when we go into TDMA, Time Division Multiple Access, then each one of these channels are divided into multiple time slots. So therefore for one sub channel, it can be divided into multiple time slots which can be shared by multiple users. So, the communication efficiency of multiple users sharing a sub channel and the overall frequency domain became much higher and much more efficient and that is one of the revolutions that were enabled through FDMA and TDMA technology combined with GSM. So evidently you can see why it became so popular worldwide. GSM services include voice communication but it also includes data transfer at 9.6 kbs per second. This is possible because we're using digital technology and digital technology is usable because we're using TDMA on FDMA architectures. You can also send Short Message Services, SMS becomes possible from here. These are the two, data transfer and SMS become the two major features that are enabled on mobile cellular phones based on second generation GSM technology. In addition, they started to use SIM cards. What is a SIM card? A SIM card is a Subscriber Identity Module. It looks something like this or when you buy a SIM card typically, it may look like the big card but then you can pop it out and have this small or that small thing pop out which you can insert into your mobile cellular phone. This is a detachable smart card. It contains user subscription information. In addition, it contains phone books. So it's so convenient. What are the advantages? Well, SIM enables a user to maintain user information even after switching cellular phones. What does that mean? Well, by changing one SIM card on a mobile phone if you have two SIM cards and you exchange it, then you exchange your phone book as well as you exchange your identification to the mobile communication service provider meaning that you can change your mobile cellular phone operator while using the same mobile phone. What does that mean? Well, it's based on what country you're in. Let's say for in the United States. I have a cellular phone and I have a SIM card and typically what you can do is that I can change the SIM card which is connected to one operator, let's say Verizon Wireless and I put in my T-Mobile SIM card into it, then I can start using T-Mobile operator communication services. That is one option. What else does this mean? Well, on the other thing, it's something like this. I have multiple phones and this is red, this is blue, this is white, and based on my fashion for the day which I'm black today, well then I may want a black phone. Then I get a black phone and I put my SIM card inside and then I have my fashion coordinated with my phone. You can do something like that. So the SIM card enables you to have this option as well as changing the phone option because it is like what SIM card you put into your phone activates that mode on your phone that is connected to the cell phone operator. Pretty cool, isn't it? And this is a major feature of GSM technology. Then we go into a more advanced system which is IS-95. This is Interim Standard 95, the first CDMA based 2G cellular standard. We're talking about CDMA. What CDMA? Well, CDMA is Code-Division Multiple Access. Meaning that instead of using FDMA and TDMA, we're going to use code to divide our sharing of the user frequency channel. So this works well against narrow band interference and multipath signal fading. So the quality of communication, the number of bit errors because we're using digital now, in second generation mobile phones, the number of bit errors can be reduced significantly. Interference is signal interference from other devices. Because there are other devices that are using the same frequency in neighboring cells, their signals can enter our cell neighboring cell and interfere with my communication that my device is having with the base station. Then this type of interference can be eliminated, most of it can be reduced by using CDMA technology. Another advantage is multipath signal fading. When I send a signal from my mobile phone to the base station, then that signal will bounce off of walls and other objects around buildings and it will arrive at the base station through multiple times making the signal smeared. In addition, the same thing is going to happen in the opposite way as well. The signal sent from the base station will reach my mobile phone through multipath fading. It will bounce off the floor, it will bounce off the wall and other places. Because of this the signal, when I send one signal, it's like I get an echo of multiple signals coming in interfering with the bit that is going to be sent afterwards. So having a long tail, having an echo isn't good and this eliminates that significantly, the multipath signal fading. The signal will fade due to the multipath signal profile and that is eliminated a lot through CDMA technology which makes the phone's much high performance. cdmaOne is a brand name for IS-95 phones that were developed by Qualcomm. Hutchison launched the first commercial cdmaOne network in Hong Kong in 1995. IS-95 traffic channels support voice or data up to bit rates of 14.4 kbs per second. Then we go into UMTS, Universal Mobile Telecommunication Systems. This is now entering third-generation and the evolution of GSM technology was used in UMTS. This is good having an evolution is good because if your technology is an evolution of the former technology, then when you go into a mobile area, a cellular communication area that can support UMTS, that's great. But what if UMTS was not installed in the overall area of the cellular region. What if it was only installed in the high density, highly populated areas and the other areas that are less populated had the former 2G technology either IS-95 or GSM. Then having a protocol on evolution of former technology means that when you don't have UMTS, then if your device can find a GSM connectivity, it will use GSM. But when it goes into an area that UMTS is available, then it will use UMTS instead of GSM. That is the option you have and that's really good and you get this from having your protocol, you can get it from having your standard, an evolution of a former standard. We call this back compatibility and it's wonderful and of course in your phone that you're using right now, there are these back compatibility options as well. UTRA is a supporting technology of UMTS where it is UMTS Terrestrial Radio Access which supports several different terrestrial air interfaces. Multiuser Access in UTRA can be supported by UTRA-FDD and TDD. FDD stands for Frequency Division Duplex and TDD stands for Time Division Duplex. This is a more advanced technology than FDMA and TDMA, meaning that FDMA advancements are shown in FDD and TDMA advancements are shown in TDD. Then, we have Wideband Code Division Multiple Access, WCDMA. This is a third-generation mobile cellular system that uses UTRA-FDD mode. It is based on the 3GPP Release 99 standard and it can send up two megabits per second data rate. As you can see, now that we entered the third-generation standard before we were at tens of kilobits per second of the data rate that we could do, but now that we enter 3G, third-generation mobile cellular communication, we are now seeing data rates at megabits per second levels. This is great. So, we are now in a new dimension of data connectivity. The first commercial WCDMA opened in Japan in 2001. Seamless mobility for voice and packet data applications were supported. Quality of service differentiation for high efficiency of service delivery was enabled, and simultaneous voice and data support was possible. These two components are very important. Meaning that quality of service differentiation means that if you have a user that needs to have a higher data rate or a better quality of service, then it will be able to support it. This new technology enables you to control, to give priority or give better services to a specific user using a certain application. In addition, it supports voice and data together at the same time. Meaning that you can send data and voice together. Meaning that during a phone call, you can receive text messages and things like that, and that's really good. It interworks with existing GSM networks. This back compatibility of course comes from that WCDMA is a evolution of GSM technology. In addition, it is backwards compatible, which is really needed. CDMA2000 is a third-generation mobile cellular system. It was standard by 3GPP2. We'd seen 3GPP on the former former page which is the Third Generation Partnership Project. This is the group that standardized third-generation mobile cellular communication, and there is a version two of this standard here. CDMA2000 is an evolution of IS-95 cdmaOne. It uses CDMA and TDMA. CDMA is Code Division Multiple Access. The wideband CDMA on the former slides was wide-band because the bandwidth given for CDMA technology was wider than five megahertz. Here, if it's narrower than five megahertz, we just call it CDMA, and this is what this technology uses. Initially, it was used in North America and South Korea. We have then 1xEV-DO added onto CDMA2000. This is EV-DO stands for Evolution-Data Optimized. Meaning that we are trying to add on an optimized data communication technology as an evolution of CDMA2000, and it enables 2.4 megabits per second of a data rate across the mobile cellular network. Here, it was launched in South Korea in January of 2002. Looking into further details, this is regarded as the first 3G system based on ITU standards. In other words, in order to become and be acknowledged as a formal 2G, 3G, or 4G, or 5G technology, then you need to be certified, and in that certification there are certain levels of performance in data rate and other features that you need to satisfy. Based on that, when it comes to third-generation mobile cellular phone technology CDMA2000 1X EV-DO was the first device technology that was officially certified by the ITU that this is performing at a level of third-generation requirements. The ITU stands for International Telecommunication Union. This is the specialized agency for information and communication technology of the United Nations. Now, among the ITU agency, there is a -T, a sector for telecommunications standardization. That is why when you see third-generation, fourth-generation, or fifth-generation technology, you will see ITU-T standardized or ITU-T approved, certified will be the terminology that you'll see, and therefore it will be ITU with a -T. Then we have HSDPA, which is High-Speed Downlink Packet Access. This is an enhanced 3G mobile communication protocol. It is an evolution of UMTS for higher data speeds and capacity. It belongs to the HSPA family of protocols. HSPA is High-Speed Packet Access. So, in High-Speed Packet Access, you can have High-Speed Downlink Packet Access, and also there's HSUPA which is High-Speed Uplink Packet Access. Now, downlink is, from a base station, the signal comes down to your mobile cellular device, that's called downlink. Typically because base stations are located on big towers or on top of buildings, so their location is higher and they're connected to the backbone network. So therefore, they are a higher entity both in location and connectivity to the network. So, we call from base station coming down to the mobile device, this is downlink, and the signal that you're mobile cellular phone device sends to the base station, that's called uplink. Of course, in some cases, the base station is located at a lower position than the mobile device user, that could happen of course. High-Speed Downlink Packet Access had its commercial network available in 2005. The peak data rate is at 14 megabits per second, that's based on Release 5. As you can see now, the data rates are going into the tens of megabits per second based on this new technology in 3G, advancements in 3G. We have EV-DO Revision A where the peak data rate for downlink is 3.1 megabits per second and the uplink is 1.8 megabits per second. Both downlink and uplink are in the megabits per second range. This was launched in the United States in October of 2006, and this is an example of some representative mobile cellular phones, and one major feature is voice over IP supported based on low latency and low bit rate communications. Now, voice over IP is having your voice sent over the traditional network, but you have the option of voice over IP. Means that your voice signals can be put on IP packets and transferred as well. So, you have the traditional network of TDMA-based voice communication on your backbone network or you can use the IP-based Internet type connectivity in the mobile cellular network. This means that based on this technology being implemented, starting from third-generation mobile communication, cellular networks, they had both the traditional base TDMA for voice support but also they had the IP-based network connectivity supported as well. These network technologies are called GERAN for the traditional one and UTRAN for the IP-based technology, and third-generation mobile networks have these two networks overlaid in areas to support both non IP-based technology but also IP-based technology. Also, we have IP-based data, but now we have IP-based also for voice. That's the voice over IP you see right there. Going into further details. Enhanced access channel MAC, that's Medium Access Control where decreased connection establishment time is enable. Multi-user packet technology enables the ability for more than one user to share the same time slot. Now, we did talk about having frequency channels divided by FDMA, and then in one subchannel, we had time slots for TDMA where a user was assigned an occasional, a periodic time slot to use for uplink and downlink. Now we're talking about, even for one of those time slots, there are ways such that that could be shared for multiple users. So, automatically, the efficiency that we have of using the same channel goes up because we now have sharing of resources which is great. The Quality of Service flags included for Quality of Service control. Meaning that there were flags that were used inside such that you can control assignments of Quality of Service. Now, I do need to mention that channel Mac, Medium Access Control, this is use such that you can share the same time slots. Medium Access Control is a technology where you look at a certain resource of time, space, or frequency, or code and you make a decision how to use that intelligently such that you do not mess up other users. You do not interfere with them such that you can accomplish communication while they're accomplishing their communication needs. That is the technology of Medium Access Control which means MAC, and using that, we have time-sharing of time slots available. Looking into HSPA+. Having that small plus at the end automatically should mean that it's better. Well, Evolved High-Speed Packet Access, it has that word evolved based on that plus that we have there. HSPA+ all IP network first launched in Hong Kong in 2009. Meaning that now we have this mobile cellular network is all IP-based. So, we can interface that IP base network very conveniently with the Internet in that area. HSPA+ uses wideband CDMA, which is UMTS based 3G technology and it's enhancements. HSPA+ is a HSPA evolution. Automatically you know that just from the name. The peak data rate goes to 168 Mbps for the downlink, from the base station to your mobile cellular phone, and the uplink is 22 Mbps. Now, the evolution is evident here. The peak data rate, you see the data rates right here are now going into hundreds of megabits per second supported for the downlink from the base station to the mobile cellular device. The uplink are comfortable in the range of the tens of megabits per second second as well. That is from the mobile device up to the base station. You may be thinking, why is the downlink always larger than the uplink? That is because the downlink is a signal that is sent from the base station to your mobile cellular device. The base station has a lot more power, it is placed on a higher location commonly, means that it has a better channel in front of it to send down to the mobile cellular device. So therefore higher data rates can be accomplished due to these advantages. Where the uplink is the signal from the mobile cellular device up to the base station, the mobile cellular device has a small battery, it cannot send signals that strong because it's nearby it's human user which you need to be aware of radiation issues. Also its position is lower, it may be between or inside a building as well. So, the signal reception back towards the base station is not as good. That's why the uplink number of data rate, the size of the data rate is always lesser than the downlink. What enables this higher performance? It is MIMO technology, or they say MIMO technology. This is Multiple-Input, Multiple-Output. What are the multiples? These are the number of antennas that are applied to the communication link. As in terms of we have multiple antennas used at the receiver as well as the transmitter to coordinate communication. Why MIMO? MIMO uses uncorrelated multiple antennas both at the transmitter and receiver to increase the data rate while using the same signal bandwidth as a single antenna system. From this statement you can tell that, before, on your mobile cellular phone it used only one antenna, and at the base station, the base station may have multiple antennas but only one of those were used to send a signal, and receive a signal with you. So therefore we had one antenna and one antenna communicating with each other to support the needs that we had for all of the former communication techniques. But starting from this, it uses the MIMO or MIMO technology which enables a higher performance through multiple antennas. Meaning that now I have multiple users sharing multiple antenna sets at my mobile device as well as the base station, this is well coordinated in here to accomplish much higher data rates. Now, please note that this data rate is the peak data rate. Meaning that this is the maximum data rate that can be sent for users. So therefore, the peak data rate may not be exactly what you get supported for your mobile device. This technology may share this peak data rate among multiple users flexibly. The higher data rate is accomplished by MIMO technology which uses multiple antenna techniques. It uses also high order modulation 64 QAM. Now, 64 QAM is a technology where each symbol that I send has multiple bits 64 symbols recorded inside where I select one of those 64 to represent a bunch of bits that are sent together in one transmission symbol. Typically when you say 64 QAM, two to the power of eight is 64. That means that I have eight bits or one byte is actually mapped into one modulation symbol and each time I can send one of the 64 symbols which will be decoded into eight bits per byte. Dual-Cell HSDPA is used to combine multiple cells into one. EV-DO Revision B was first deployed in Indonesia in 2010. It is a Multi-Carrier evolution of Revision A. High data rate per carrier as well as downlink peak can go up to 4.9 Mbps per carrier. The uplink peak can go up to 1.8 Mbps per carrier. EV-DO Revision B performs well because it has reduced latency from statistical multiplexing across channels. What that means is that without statistical multiplexing in the former version of it, when you have multiple channels that needed to send data, well in that case they were assigned certain slots and these slots were dedicated to users. Well, if a user did not have anything to send, that slot would have been empty and it would have been wasted. In statistical multiplexing what they do is that, the devices that have something to send, they send it and it gets stacked up and whoever has something in request in the queue, that gets sent in that order. So, therefore there are almost no wasted slots based on statistical multiplexing. So therefore the efficiency of using the resources goes up which is great. This means that it has reduced delay and improved quality of service. Longer talk-time and standby time is enable. Hybrid frequency re-use and reduced interference at cell edges and adjacent sectors were enabled through EV-DO Revision B technology. So therefore at the cell edge, the quality of service is enhanced significantly. More efficient asymmetric data rate support. Once again, asymmetric means that the downlink and uplink data rates are not the same. Of course this is the case and you can even have a higher flexibility of asymmetric capability where you can increase the downlink even more or reduce it to support a little bit more on the uplink data rate. Asymmetric services come from file transfer, web browsing, multimedia content delivery, and other places. Just for example, when you're browsing a Website, you may not have downlink all the time. Well then when you have something to download you need a lot of download capacity, but after you downloaded that onto your device, you may not have much to download further. Then in that case, the uplink can take advantage of the leftover capacity to send more at a faster data rate back from the mobile device up to the base station. Long-term evolution is our next topic and a lot of devices that are available now are based on this technology. This was launched in North America in 2010 with the Samsung SCH-R900. This was deployed on both GSM and CDMA mobile operators. So therefore it has backward compatibility with 3G and 2G devices and networks. The peak data rate based on Release 8 is a downlink of 300 Mbps and an uplink of 75 Mbps. As we can see that the peak data rate ranges have gone up significantly where the data rates are in the larger hundreds of megabits per second for download and at a large rate for the uplink as well in the 75 Mbps range. Then we had LTE-A, which is LTE-Advanced. From this standard, this is considered fourth generation and it is based on the ITU-R IMT-Advanced process. Based on this overall category, this technology has a peak data rate based on Release 10 of 3 Gbps downlink and uplink is 1.5 Gbps. As you can see, reaching in the fourth generation mobile communication puts us into peak downlink and uplink data rates that are in the range of gigabits per second. So, from kilobits per second in the second generation, we went into megabits per second, and tens of megabits per second in the third generation, now we're going into the fourth generation which now enters the range of gigabits per second. In the following lectures, I'm going to talk about the details of LTE, LTE-A and the future of fifth generation 5G mobile communication technology in further detail. LTE-A incorporates high order MIMO technology using 4x4 antennas and more. Meaning that on the mobile device you have four antennas and at the base station you have four antennas or more. This allows multiple carriers to be bonded into a single stream and that is how we get gigabits per second data rates for uplink and downlink. These are the references that I used. In my following lectures, I'm going to focus more on LTE, LTE-A which is fourth generation mobile communications and the future of fifth generation mobile communications, 5G. So please, go into the details of those because that's the future and that's where all the money is going to be invested in for high advanced mobile communication services. I'll go into the details of that. Thank you very much.
