A method executed by a network node for determining a length of a virtual cell index field to be transmitted with downlink control information, DCI, the virtual cell index field length for transmitting a virtual cell index to a wireless device being dynamically settable, the method comprising: determining a number of configured virtual cell identities, IDs; transmitting the configured virtual cell identities to the wireless device via Layer 3, L3, signaling; the method further comprising: when the number of configured virtual cell IDs is greater than one: selecting a virtual cell index corresponding to a particular one of the virtual cell IDs; setting the virtual cell index field length based on the number of virtual cell IDs; and transmitting the selected virtual cell index in the virtual cell index field to the wireless device; when the number of configured virtual cell IDs is zero, setting the length of the virtual cell index field to be of length zero and transmitting no virtual cell IDs to the wireless device, thereby causing the wireless device to use a physical layer cell identity to generate a pseudo-random sequence when the number of configured virtual cell IDs is one, setting the length of the virtual cell index field to be of length zero and transmitting a single virtual cell ID to the wireless device, thereby causing the wireless device to use the single virtual cell ID to generate a pseudo-random sequence. determining a number of configured virtual cell identities, IDs; transmitting the configured virtual cell identities to the wireless device via Layer 3, L3, signaling; the method further comprising: when the number of configured virtual cell IDs is greater than one: selecting a virtual cell index corresponding to a particular one of the virtual cell IDs; setting the virtual cell index field length based on the number of virtual cell IDs; and transmitting the selected virtual cell index in the virtual cell index field to the wireless device; when the number of configured virtual cell IDs is zero, setting the length of the virtual cell index field to be of length zero and transmitting no virtual cell IDs to the wireless device, thereby causing the wireless device to use a physical layer cell identity to generate a pseudo-random sequence when the number of configured virtual cell IDs is one, setting the length of the virtual cell index field to be of length zero and transmitting a single virtual cell ID to the wireless device, thereby causing the wireless device to use the single virtual cell ID to generate a pseudo-random sequence. when the number of configured virtual cell IDs is greater than one: selecting a virtual cell index corresponding to a particular one of the virtual cell IDs; setting the virtual cell index field length based on the number of virtual cell IDs; and transmitting the selected virtual cell index in the virtual cell index field to the wireless device; selecting a virtual cell index corresponding to a particular one of the virtual cell IDs; setting the virtual cell index field length based on the number of virtual cell IDs; and transmitting the selected virtual cell index in the virtual cell index field to the wireless device; when the number of configured virtual cell IDs is zero, setting the length of the virtual cell index field to be of length zero and transmitting no virtual cell IDs to the wireless device, thereby causing the wireless device to use a physical layer cell identity to generate a pseudo-random sequence when the number of configured virtual cell IDs is one, setting the length of the virtual cell index field to be of length zero and transmitting a single virtual cell ID to the wireless device, thereby causing the wireless device to use the single virtual cell ID to generate a pseudo-random sequence.