Long term evolution (LTE) is the standard for today’s wireless networks, and replaces third generation (3G) technology. LTE technology is a based on a 3GPP standard that provides for a downlink speed of up to 150 megabits per second (Mbps) and an uplink speed of up to 50 Mbps. LTE protocol is held to 3GPP’s high standards and must be tested accordingly. This provides the need for LTE protocol testing equipment.
What is LTE Protocol?
LTE protocol stack functions consist of the Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Radio Resource Control (RRC). LTE is the latest generation of the 3GPP standards. The LTE standard specifies an IP-only network supporting data rates up to 150 Mbps. These high data rates will enables new applications and services such as voice over IP, streaming multimedia, videoconferencing or even a high-speed cellular modem. [1]
“The LTE standard grew out of the Global System for Mobile Communications (GSM) and Universal Mobile
Telecommunications System (UMTS) standards, commonly called 3G. Voice communication was primary application,
with data added recently. Mobility and seamless handoff were requirements from the start, as was a requirement for
central management of all nodes. LTE speeds will be equivalent to what today’s user might see at home on a fast cable modem. The LTE standard is designed to enable 150 Mbps downlink and 50 Mbps uplink over a wide area. While 150 Mbps is LTE’s theoretical top uplink speed, each user’s bandwidth will depend on how carriers deploy their network and available bandwidth.” [1]
How to Test LTE Protocol?
Engineers should perform protocol tests along with a functional test to ensure that the protocols function properly and comply with the 3GPP LTE specifications. Engineers should also address performance aspects, such as whether the product can handle the high-data-rate requirements of LTE. [2]
“Depending on the degree of integration, you can use various approaches for performing protocol tests. Several test-equipment manufacturers offer test instruments that include software-based LTE protocol testers. If a layer-1 implementation is not yet available, or integration has not yet taken place, you can use this software to perform a virtual test of the protocol software. In the R&S CMW500 for LTE, for example, the test software emulates the behavior of the protocols on the network end. Developers can connect the protocol stack to be tested to a virtual tester via an IP connection. LTE test scenarios then verify the behavior of the protocol stack on the wireless device end. These scenarios can include a simple connection setup or more complex reconfigurations. All important functions of the layer-2 and layer-3 protocols can be verified in the virtual test environment of the CMW500, for example.” [2]
After layer-1 integration, the wireless device or chipset can be connected to a bench protocol tester for even further testing. This can take place though the RF or in the baseband. You can then subject the device under test (DUT) to the LTE test cases to study the behavior of the device and detect possible errors. [2]
When moving to the hardware of LTE protocol testing, developers can reuse the scenarios from the virtual-test environment. “The R&S CMW500 for LTE also provides test cases that include layer-1 functionality. Of particular interest are the test cases that require an interaction between the downlink and uplink, such as MIMO or the hybrid automatic repeat request (ARQ) protocol.” [2]
For throughput measurements, it’s important to connect to the user platform and test those functions, such as video. Actual user data can also be processed in the protocol test scenario. At the end of the day, LTE devices must be able to work with other technologies, as LTE has not been rolled out everywhere as of yet. [2]
[1] Freescale, Long Term Evolution Protocol Overview, http://www.freescale.com/files/wireless_comm/doc/white_paper/LTEPTCLOVWWP.pdf
[2] EDN, Protocol Stack Testing for LTE, http://www.edn.com/design/test-and-measurement/4381444/Protocol-stack-testing-for-LTE
