Data Transfer Rate Comparison

Transcription

1 LTE Broadband and Public Safety David Fein, Project Manager November 2011 Executive Overview Long Term Evolution (LTE) is a relatively new standard for wireless communications, adopted by commercial and public safety users. LTE is commonly referred to in the commercial communications world as 4G standing for Fourth Generation. The intent of the LTE standard is to provide wireless communications at much faster speeds and better reliability than is currently available. LTE is the standard that has been adopted for the Public Safety D Block 700 MHz frequency spectrum. An LTE network would operate in a similar fashion to the commercial carriers 4G cellular communications network. The intent of this paper is to give the public safety end user an idea of what LTE is and can offer. Understanding LTE LTE is currently being deployed by Verizon Wireless and AT&T in the US. Sprint has indicated that they will be following suit with LTE as their 4G protocol. Long Term Evolution (LTE) is a 4G wireless broadband technology and is part of 3GPP (GSM) and 3GPP2 (CDMA) open standards. Approximately 90% of the estimated 5 billion worldwide cellular subscribers are using 3GPP and 3GPP2 technology and are very likely to migrate to LTE. The network operates from the Radio Frequency side in the same manner as a cellular telephone network; comprised of a main switch, a backhaul network connecting cells, cell sites, and subscriber devices. From the network side it is an all Internet Protocol (IP) solution and does not have the circuit switched voice channel like trunked Land Mobile Radio or 2G and 3G cellular systems. The LTE system has a lofty goal of achieving 100 MB/s data transfer rates between a subscriber device and the user s target application. 30 Data Transfer Rate Comparison Data Transfer Rate MB/s 5 0 FAX Dial Up DSL Cable 3G 4G LTE Modem Mobile Mobile

2 Note that LTE also includes a Self Organizing Networks (SON) feature allowing automatic coordination of capacity and coverage between macro, micro, pico, and in building networks. This could be a benefit to Public Safety when additional mobile cell site units are brought to use in disaster recovery incidents. Global wireless service providers are just starting to deploy LTE commercially. It is the first time that a standard has been adopted and implemented universally for next generation communications. Until now, there have been two competing standards that are not compatible with each other, CDMA and GSM. Code Division Multiple Access (CDMA), was the brainchild of Qualcomm in the USA, and was adopted by approximately 25% of the mobile device users in the world. Verizon Wireless is the largest CDMA based carrier in the USA. Global System for Mobile communications (GSM) was developed by a consortium of European service providers and equipment manufacturers. AT&T wireless is the largest US carrier utilizing GSM. GSM is a time sliced data transmission protocol, similar to a serial data port on a computer, the data is pushed along one bit at a time, and collected at the other end and strung back together. CDMA is similar to a parallel port on a computer, dividing the data into digital words that are transmitted simultaneously on adjacent channels, collected at the other end and put back together. The major differences between 2G/3G and 4G LTE are latency, IP, data speed, Multi Media Broadcast/Multicast Service (MBMS), and the Self Organizing Network. Latency is the delay in the system from the time a user initiates an activity to when the activity occurs. For instance on a push totalk system, from the time the button is pushed to when the network recognizes the signal and connects the user is the latency in the system. The 4G LTE systems have less than 20ms of latency. Internet Protocol is the standard for the 4G system, all the traffic on the system is converted from voice to IP and moved through the network very efficiently this way. MBMS is the ability of the system to allow multiple users to listen to or watch the same transmission for efficient group communications. Selforganizing networks allow for the addition of temporary nodes to be easily deployed at an event or incident. The main gateway node is known as the Evolved Packet Core or core for short. One core could easily manage all of the State s public Safety users. As an example, Verizon is currently operating two cores in the US for its LTE system, which will carry them through the entire conversion to 4G. The core does the data handling for all the subscriber devices and cell sites. It is also the conduit to the Internet, and any private networks that need access to the system. The cost to purchase a core is roughly $3M, plus a place to house it and a very high speed connection to the internet. The backhaul network is a key part of the infrastructure of the LTE system. The higher data rates, potentially times what we experience now, are dependent on a wide and fast pipeline to move data from the core to the cell sites and out to the subscriber devices. For comparison, once the network is loaded, the demand for the backhaul network will be times what it is today, and as users get used to the amount of data that they can obtain, it may go up another order of magnitude. A Cell site in the LTE network is known as an enodeb. The enodeb is what we know as a base station, providing the digital to Radio Frequency (RF) conversion. The configuration of the enodeb is the same as a typical cell site, three sectors covering 120⁰ each. The major difference between a standard cell site

3 and an enodeb is the number of antennas per sector. LTE utilizes Multiple Input Multiple Output (MIMO) transmission techniques that require antenna diversity. There may be up to eight antennas per sector. The MIMO technique allows the beam of the antenna to be shaped and directed, much like military radar can track multiple targets, the enodeb can track multiple subscriber devices and optimize the beam width and power for the best connection. A close in device does not require the same amount of power to receive a signal that one on the edge of the cell does. The faraway device can benefit from a narrower beam concentrating more power on it. Subscriber Devices are rolling out with dongles for mobile computing first, then smartphone devices. The dongle is a device that connects to the computer via USB. It is a full radio with MIMO and the electronics to convert the computer s Internet Protocol (IP) data to RF. Since 3G has been implemented, smartphones have been using IP for data transfer, including voice telephony. The leap for these devices to 4G or LTE is the addition of the MIMO hardware and the increased processor speed and memory it takes to keep up with higher data transfer rates. Some devices have already been fielded, the trend is that handheld devices will continue with a large screen and either a soft keyboard integrated with the display, or a sliding mechanism to access a fixed keyboard. The downside to more processor, memory and increased data rates is battery life. Typical 3G devices can go 8 10 hours of use before a charge is required, the LTE/4G devices are averaging four hours. The dongle gets its power from the USB port on the PC, so it is not limited by an internal battery, just what the PC can handle. Typical notebook PC s average 2 4 hours of battery life. Data Rates LTE uses some of both the CDMA and GSM technologies to maximize data transfer to and from the mobile device. The new twist is that the link from the enodeb to the subscriber uses a different transmission technique from the subscriber device to the enodeb. The engineers behind the system have broken away from the paradigm of using the same protocol for the uplink as the downlink. Generally the downlink from the network to the subscriber device is times more data than the uplink. The benefit of this technique is that the downlink from the enodeb to the subscriber unit can take advantage of the fixed antennas and beam shaping and power control to transmit more data than an equivalent fixed beam configuration. The data rates required to meet the standard are 768 KB/s at the edge of the cell, and up to 100 MB/s close to an enodeb. For comparison, a DSL wired connection is capable of 6 MB/s, a cable modem connection is typically MB/s, and typical cellular data transmission ranges from 100 KB/s to 1MB/s. Coverage From our experience with narrow banding of the VHF systems, we learned that the power output of repeater sites has been limited to prevent interference on adjacent channels. This has affected the coverage footprint of particular sites, not so much outside of buildings, but inside structures and between buildings. LTE may have some of these same issues; in building penetration will not be what we are used to with current Cellular systems. The user community has been installing in building

4 systems for over ten years. The service providers do not have plans to start with the same level of inbuilding coverage for LTE. Most of the initial devices that are shipping or planned still have 3G radios and Wi Fi built in for supplemental coverage. Typically, if one were to field an independent network, using the cellular system layout as a guide would be a safe starting point for sizing the network, number of sites and location. Co Locating LTE enodeb s with existing cell sites could save some time and construction costs. Infrastructure The infrastructure demands are much higher with higher data rates. With projected downlink rates of 100 MB/s per user, the amount of data being moved increases dramatically. Whatever is in place now will not be enough to support LTE. A typical data connection to a 3G cell site is a T1 line capable of MB/s, sufficient for most voice calls and data transmission. To provide tens of users per sector with 100 MB/s data rates, the T1 is no longer an option, a direct multimode fiber capable of 1 GB/s data rates will be required to transfer data to and from the core. A major upgrade to the backhaul network is required, plus the ability to bring fiber to each enodeb. Nevada currently has a mix of microwave links, T1 s, and fiber to achieve the backhaul for today s data needs. The other big question is what data is going to be delivered? Having a huge data pipeline capable of delivering just about anything to anyone is great. Most of the demonstrations presented have shown simultaneous web surfing, streaming video, and voice teleconferencing. That is a lot of data, how much of it is relevant to an end user? Is there a central database of everything that should be shared? What should be shared? With whom? Who controls access? Who provides the data? What about governance? All of these things need to be worked out ahead of an LTE implementation. Recommendations from system operators have centered on a central board that sets the standards for data use and user access, and what data is available. Public/Private Partnership An interesting development in the LTE world is that Public Safety has something that the commercial providers can t get: Bandwidth. The D Block looks like it will be assigned to Public Safety. It is adjacent to the private sector s assigned bandwidth for implementing LTE/4G. The private sector is interested in discussing the dual use of the public safety spectrum. Generally, what they propose is to have the private service providers build out their networks with enodeb infrastructure capable of covering their own spectrum plus the D Block. In exchange for use of the bandwidth for non public safety use, the LTE network would be available sooner and at a lower cost. Ruthless priority on the D Block side would be enforced, with priority going to public safety. Additional advantages are provisioning of mobile devices and a reduction in overhead to manage the system. Control, access, and security are three major concerns of any network manager. More so for the public safety side as the data that will be requested and provided to subscriber devices is sensitive and may even be classified. Provisioning subscriber devices is more complex than a Land Mobile Radio system. Each device is coded specifically to a user with conditions on its use. This is great for flexibility and control of data access, but a nightmare to provision for a network manager. Think of all the changes

5 that go on daily in our organizations and how to manage it. Fortunately the service providers deal with this on a much larger scale every day. They have systems and procedures in place to deal with managing these transactions, and the impact on their infrastructure is minimal. Once provisioned, a user s device would give them access to what they need as determined by their function and supervision. Infrastructure Suppliers and Network Providers Appendix A contains a brief list of infrastructure manufacturers with some of their capability, it is by no means comprehensive, just an idea of what some of the major players are capable of today. Appendix B contains a brief list of network service providers and their current capability, again, not a complete comprehensive list, just an overview. Future LTE Public Safety standards evolution wish list 1) Secure PTT across LTE and P25 2) Unified Services (data acquisition, permissions, network management) 3) Enhanced Public Carrier Interoperability secure roaming with agency control while on public networks, seamless roaming 4) Direct Mode (device to device) 5) Dual Mode (LTE/P25) devices Glossary LTE 4G Long Term Evolution Fourth Generation, a standard that has been adopted by cellular network providers around the world to provide digital cellular radio communications at significantly higher speeds than are available in previous generations of cellular radio communications 3G Third Generation cellular networks, identified by data rates of less than 300KB/s IP Internet Protocol, the standard by which the Internet operates. The standard covers everything from addresses for devices to data transmission and error correction. CDMA Code Division Multiple Access, a protocol developed by Qualcomm to deliver digital communications over the air in cellular radio systems, similar to a parallel communications port on a computer. The data is transmitted in uniquely coded digital words, subscriber devices have a unique key to decode data meant specifically for that device. TDMA Time Division Multiple Access, a protocol developed by a consortium of European communications companies to deliver digital data over the air in cellular radio systems, similar to a serial port on a computer. Data is delivered in a time sliced section that is coded for individual devices. Subscriber units synchronize to their unique time slice to transmit and receive data.

6 LMR Land Mobile Radio, a descriptor for a radio system primarily used for Public Safety and other users that require wireless communications between mobile and fixed sites. P25 Project 25, a standard which LMR radio systems are to use from now into the future. The Federal Government has mandated that all mobile radio system used for public safety must be P25 compatible. The standard has 219 elements that can be drawn from to develop a system. It works in a similar manner to a cellular system with a core, switch, and multiple base station sites to cover a given area. D Block A section of the radio frequency spectrum that has been suggested for exclusive use by Public Safety organizations nationwide. The intent is to have a single frequency band and a single standard protocol that would establish a nationwide high speed public safety grade network for first responders. MIMO Multiple Input Multiple Output with relation to antenna ports on base station and subscriber devices. Using MIMO allows the devices to sense the best signal path in and out of the device, optimizing signal paths and adapting instantly to changing conditions. MIMO is analogous to using two ears to hear a sound, by moving your head or adjusting the angle to the source, better reception is achieved. MIMO usually has two antennas, but can use four in certain cases. Backhaul The Backhaul part of the network is used to bring data to and from the remote cell sites. Current 3G and LMR systems typically use microwave links and twisted pair phone lines to move data back and forth to the core switches. Microwave links have data throughput limitations at the 100 MB 1GB range, depending on how close the target system is to the emitter, and environmental conditions. Phone lines are typically limited to 1 3MB/s. 4G systems are planned to deliver much higher data rates. Higher density microwave links and optical fiber will be the preferred method to transfer data in the 1 10GB/s range.

7 Appendix A Infrastructure Suppliers Alcatel Lucent is one of the pioneers of wired and wireless communication systems. They started life as the Bell System, and still carry on those traditions within the company, despite a few name changes and being acquired by the French Telecom giant Alcatel. The original cellular telephone system was developed in part by Lucent (then Bell). Alcatel Lucent has developed an open architecture system for LTE that utilizes their experience with 3G cellular systems and switching, as well as some new innovations from Bell Laboratories that involve distributed Radio Frequency transceivers and other techniques to increase data throughput in a network. Open architecture means that end user subscriber devices can be from any manufacturer that meets the standards, reducing overall cost of the system as well as increasing the variety of devices that are available for use. Alcatel Lucent currently have a fully functioning LTE network operating in Boulder, CO for the public safety users. It is in everyday use, and is available for interested parties to observe and evaluate. Harris Harris has acquired MA/COM s land mobile radio assets and is trying to leverage that acquisition for next generation systems, partnering with Nokia Siemens for their expertise on the 4G LTE communications side. Current plans are for an evolution on their VIDA IP network which we are currently taking advantage of to connect three of the four core systems in Nevada. The system is proprietary, using the VIDA network management software and system components. It is intended to integrate seamlessly with the Open Sky system. All the backhaul and transmissions are in IP. Harris recently demonstrated a cross connection between Nokia Siemen s private LTE network and a P 25 network at the Dallas Fort Worth International Airport. Harris is delivering end end 700MHz LTE networks for Public Safety. Harris is delivering LTE user terminals (for both mobile and handheld operation), LTE network infrastructure (for both LTE core and radio access), and user applications (for an integrated user experience of voice, video, and data). Harris is committed to an open standards based eco system for public safety LTE partnering with Nokia Siemens Networks (NSN) for LTE infrastructure. In addition, Harris and NSN are participating in the NIST 700MHz test bed in order to certify the interoperability of the Harris/NSN solution. Motorola Motorola was the pioneer of cellular systems fielding the first system months ahead of competition in the mid 1980 s. Motorola is a very familiar name in the Public Safety; they have been providing portable, mobile, and base station equipment for over 80 years. Motorola recently sold their infrastructure manufacturing group to Nokia Siemens. The Motorola approach to LTE is open architecture, and a partnership with Verizon Wireless, Ericsson, Alcatel Lucent, and various mobile device manufacturers. Motorola is acting as a system integrator, providing the dispatch consoles, switch

8 technology and software to tie together enodeb base stations from Ericsson and Alcatel Lucent. The unique point of interest with Motorola s approach is the public/private partnership with Verizon Wireless. Verizon has the spectrum adjacent to the public safety D Block, and has designed their RF side of the network to operate in C and D Black. The advantage to Public Safety is that the network gets built out by a cellular provider, without the need to manage radio sites and the network. Public Safety users lease the space on the network, and in the case of an emergency take ruthless priority of the D Block. With open architecture and Verizon vetting and validating devices, there should be plenty of devices available for subscribers. Verizon s 4G network is a true LTE network and already has several subscriber devices available, including two USB dongles and several handheld devices.

9 Appendix B Network Service Providers AT&T Wireless AT&T has recently made the decision to embrace 4G LTE and migrate away from the GSM/HSDPA+ protocol they had been using. They too, will be looking to offer public/private partnerships with Public Safety to boost the subscriber base. They may be distracted by the merger with T Mobile, which has yet to be approved. In the meantime, they continue to build out their network, which does not have the same level of coverage in Nevada as Verizon. Sprint/Clear Sprint had absorbed Nextel, famous for the push to talk cell phone, into their CDMA network. Sprint had focused their broadband play on WiMax, and acquired ClearWire (now Clear) to augment that strategy. Clear has an installed network and subscribers. The FCC reiterated the desire to have one nationwide network on a single standard, and named 4G LTE as that standard. This left Sprint out of the picture as the only WiMax player remaining. Sprint has just come out with a new strategy to deploy a hybrid WiMax/LTE enodeb architecture that could be used for Public Safety in the future. Verizon Wireless As mentioned earlier, Verizon Wireless is ahead of the competition as far as deploying a network on the 4G LTE standard, preparing for a play in the D Block arena, and standing up commercial service.