LTE TRAFFIC

The type of traffic carried by LTE networks can be split into the five categories listed below:

• Web Browsing:

Request-response traffic generated by end user applications like Internet

‘Explorer’ and ‘Firefox’ etc. used to browse the Internet.

• Email:

Traffic generated by reading and sending emails.

• Audio/Video Streaming:

Streaming traffic generated by end user applications like ‘Youtube’ used to view video content on the Internet.

• File Transfer:

Traffic generated by users downloading or uploading files from the Internet.

• Voice:

Traffic generated by Voice over IP (VoIP) applications like ‘Skype’ that allow users to make and receive voice calls over the Internet.

Each of these categories and their particular traffic demands are explained on the following sub-sections.

1.1.1 Web Browsing Traffic

The request for a web page produces a small uplink traffic requirement with a much higher demand on the downlink as the page is downloaded to the user. The acknowledgements and retransmission requests sent in the uplink as the page is downloaded produce a much lower traffic requirement. The time taken to download the web page and hence the ‘delay’ experienced by the user will depend on the contents of the page, number of retransmissions, bandwidth available and any latencies in the connection. The traffic generated by a user browsing three web pages and the Internet protocol stack used is illustrated in Figure 4-2 below.

Figure 4-2: Web Browsing Traffic

The user generating the traffic illustrated in Figure 4-2 above reached a peak rate of 1.36 mbps in the downlink with an average rate of 105.1 kbps and 12.3 kbps in the downlink and uplink respectively.

As illustrated in Figure 4-2 above Hypertext Transfer Protocol (HTTP) and Transmission Control Protocol (TCP) are used to carry web browsing traffic over IP. The operation of these and other Internet protocols are explained later in this chapter.

1.1.2 Email Traffic

An email user will generate frequent peaks in the downlink and uplink traffic requirement as the emails are read and sent. The duration of these peaks will depend on the size of the email and the available bandwidth. As emails are transferred to and from the user’s PC acknowledgements sent in the opposite direction also generate smaller peaks in traffic requirements. Any

retransmissions will be experienced as ‘delay’ by the user. The traffic generated by an email user reading and sending emails and the Internet protocol stack used is illustrated in Figure 4-3 below.

Figure 4-3: Email Traffic

The user generating the traffic illustrated in Figure 4-3 above reached a peak rate of 367.7 kbps in the downlink as an email was being downloaded from the server.

A slightly lower peak was reached in the uplink as an email was sent to the server. Over the course of the session an average rate of 31.8 kbps and 19.1 bps was generated in the downlink and uplink respectively.

As illustrated in Figure 4-3 Hypertext Transfer Protocol (HTTP) and

Transmission Control Protocol (TCP) are also used to carry email traffic over IP.

The operation of these and other Internet protocols are explained later in this chapter.

1.1.3 Video Streaming Traffic

A user watching streaming video from the Internet generates consistently high downlink traffic requirement as the video content is downloaded from the server.

Once a certain (configurable) buffering time has elapsed the content is shown to the user using a suitable video playing application while the remainder is being downloaded. The acknowledgements and retransmission requests sent in the uplink produce a much lower traffic requirement. Any retransmissions or bandwidth restrictions may produce a pause in the video content if all the data in the buffer has been viewed. The traffic generated by a video streaming user and the Internet protocol stack used is illustrated in Figure 4-4 below.

Figure 4-4: Video Streaming Traffic

The user generating the traffic illustrated in Figure 4-4 above reached a peak rate of 1.58 mbps in the downlink with an average rate of 830.6 kbps and 20.2 kbps in the downlink and uplink respectively.

As illustrated in Figure 4-4 above HyperText Transfer Protocol (HTTP) and Transmission Control Protocol (TCP) are also used to carry video streaming traffic over IP. The operation of these and other Internet protocols are explained later in this chapter.

1.1.4 File Download Traffic

A user downloading or uploading a file from or to the Internet produces a constantly high traffic requirement in the direction that the file is transferred.

The acknowledgements and retransmission requests sent in the opposite direction as the file is transferred produce a much lower traffic requirement. Any

retransmissions or bandwidth restrictions increase the time required to download or upload the file. The traffic generated by a user downloading a file from the Internet and the Internet protocol stack used is illustrated in Figure 4-5 below.

Figure 4-5: File Transfer Traffic

The user generating the traffic illustrated in Figure 4-5 above reached a peak rate of 1.53 mbps in the downlink with an average rate of 650 kbps and 14.2 kbps in the downlink and uplink respectively.

As illustrated in Figure 4-5 above File Transfer Protocol (FTP) and Transmission Control Protocol (TCP) are used to support file transfer over IP. The operation of these and other Internet protocols are explained later in this chapter.

1.1.5 Voice Traffic

A voice over IP (VoIP) call, unlike the previous traffic types produces a near symmetrical but relatively small traffic requirement. Since latency is an important consideration in conversational traffic there is no retransmission mechanism employed by the higher layers, however the LTE HARQ mechanism will use retransmissions to correct errors in the air interface in the same manner as all other traffic. The traffic generated by a Voice over IP (VoIP) call and the Internet protocols used is illustrated in Figure 4-6 below.

Figure 4-6: Voice Traffic

The user generating the traffic illustrated in Figure 4-6 above reached a peak rate of 39 kbps in the uplink with an average rate of 21.4 kbps and 24.7 kbps in the downlink and uplink respectively.

A 3-minute speech call will generate approximately 1 MB of combined uplink and downlink data as illustrated in Figure 4-6 above.