A control node (20, 20-2) in a cellular communication system comprising: one or more communication interfaces (30, 32) configured to communicatively couple the control node to a first communication node (12, 12-1) and a core network; and a processing subsystem associated with the one or more communication interfaces configured to: - receive, in association with a call between the first communication node and a second communication node (12 12-2), a wideband encoder mode request indicator and a preferred narrowband encoder mode request from a second control node (20, 20-1) for the second communication node; - receive encoded speech from the second control node as a payload of a Real Time Protocol, RTP, packet, wherein the wideband encoder mode request indicator and the preferred narrowband encoder mode request from the second communication node are included in a payload header of the RTP packet; - select a desired encoder mode such that: a wideband encoder mode is selected as the desired encoder mode if the wideband encoder mode request indicator indicates that the second control node has requested the wideband encoder mode and a voice encoder (16-1, 16-2) of a vocoder (14, 14-1, 14-2) of the first communication node is capable of operating in the wideband encoder mode; and one of a plurality of narrowband encoder modes identified by the preferred narrowband encoder mode request is selected as the desired encoder mode if either the wideband encoder mode request indicator indicates that the second control node has not requested the wideband encoder mode or the voice encoder of the vocoder of the first communication node is not capable of operating in the wideband encoder mode; and - send the desired encoder mode to the first communication node. one or more communication interfaces (30, 32) configured to communicatively couple the control node to a first communication node (12, 12-1) and a core network; and a processing subsystem associated with the one or more communication interfaces configured to: - receive, in association with a call between the first communication node and a second communication node (12 12-2), a wideband encoder mode request indicator and a preferred narrowband encoder mode request from a second control node (20, 20-1) for the second communication node; - receive encoded speech from the second control node as a payload of a Real Time Protocol, RTP, packet, wherein the wideband encoder mode request indicator and the preferred narrowband encoder mode request from the second communication node are included in a payload header of the RTP packet; - select a desired encoder mode such that: a wideband encoder mode is selected as the desired encoder mode if the wideband encoder mode request indicator indicates that the second control node has requested the wideband encoder mode and a voice encoder (16-1, 16-2) of a vocoder (14, 14-1, 14-2) of the first communication node is capable of operating in the wideband encoder mode; and one of a plurality of narrowband encoder modes identified by the preferred narrowband encoder mode request is selected as the desired encoder mode if either the wideband encoder mode request indicator indicates that the second control node has not requested the wideband encoder mode or the voice encoder of the vocoder of the first communication node is not capable of operating in the wideband encoder mode; and - send the desired encoder mode to the first communication node. - receive, in association with a call between the first communication node and a second communication node (12 12-2), a wideband encoder mode request indicator and a preferred narrowband encoder mode request from a second control node (20, 20-1) for the second communication node; - receive encoded speech from the second control node as a payload of a Real Time Protocol, RTP, packet, wherein the wideband encoder mode request indicator and the preferred narrowband encoder mode request from the second communication node are included in a payload header of the RTP packet; - select a desired encoder mode such that: a wideband encoder mode is selected as the desired encoder mode if the wideband encoder mode request indicator indicates that the second control node has requested the wideband encoder mode and a voice encoder (16-1, 16-2) of a vocoder (14, 14-1, 14-2) of the first communication node is capable of operating in the wideband encoder mode; and one of a plurality of narrowband encoder modes identified by the preferred narrowband encoder mode request is selected as the desired encoder mode if either the wideband encoder mode request indicator indicates that the second control node has not requested the wideband encoder mode or the voice encoder of the vocoder of the first communication node is not capable of operating in the wideband encoder mode; and a wideband encoder mode is selected as the desired encoder mode if the wideband encoder mode request indicator indicates that the second control node has requested the wideband encoder mode and a voice encoder (16-1, 16-2) of a vocoder (14, 14-1, 14-2) of the first communication node is capable of operating in the wideband encoder mode; and one of a plurality of narrowband encoder modes identified by the preferred narrowband encoder mode request is selected as the desired encoder mode if either the wideband encoder mode request indicator indicates that the second control node has not requested the wideband encoder mode or the voice encoder of the vocoder of the first communication node is not capable of operating in the wideband encoder mode; and - send the desired encoder mode to the first communication node.